Get Started

Installation

cargo add leptos-use

Examples

• Examples Directory

Usage Example

Simply import the functions you need from leptos-use

use leptos::prelude::*;
use leptos_use::{use_mouse, UseMouseReturn};

#[component]
fn Demo() -> impl IntoView {
    let UseMouseReturn { x, y, .. } = use_mouse();
    
    view! { cx,
        {x} " x " {y}
    }
}

Please refer to the functions list for more details.

Stable Rust

Just like leptos this library can be safely run on stable rust. In the Getting Started section of the leptos docs you can read more about what this means.

Options

Most functions in Leptos-Use come with a version ..._with_options. For example use_css_var has a version use_css_var_with_options. As the name suggests, you can provide additional options to those versions of the functions.

These options are defined as structs with the corresponding PascalCase name. For our example use_css_var_with_options the name of the struct is UseCssVarOptions. Every option struct implements Default and the builder pattern to make it easy to change only the values needed. This can look like the following example.

#![allow(unused)]
fn main() {
let (color, set_color) = use_css_var_with_options(
    "--color",
    UseCssVarOptions::default()
        .target(el)
        .initial_value("#eee"),
);
}

Here only the values target and initial_value are changed and everything else is left to default.

TODO : automatic conversion like Fn and Option

Element Parameters

Many functions in this library operate on HTML/SVG elements. For example, the function use_element_size returns the width and height of an element:

#![allow(unused)]
fn main() {
use leptos::{*, html::Div};
use leptos_use::{use_element_size, UseElementSizeReturn};

#[component]
pub fn Component() -> impl IntoView {
let el = NodeRef::<Div>::new();

let UseElementSizeReturn { width, height } = use_element_size(el);

view! {
    <div node_ref=el></div>
}
}
}

In the example above we used a Leptos NodeRef to pass into the function. But that is not the only way you can do that. All of these work as well:

#![allow(unused)]
fn main() {
use_element_size(window().body()); // Option<web_sys::Element>
use_element_size(window().body().unwrap()); // web_sys::Element
use_element_size("div > p.some-class"); // &str or String intepreted as CSS selector

pub fn some_directive(el: HtmlElement<AnyElement>) {
    use_element_size(el); // leptos::html::HtmlElement<T>
}
}

Signal of Strings: Signal<String>, ReadSignal<String>, RwSignal<String>, Memo<String>; also works with &str:

#![allow(unused)]
fn main() {
let (str_signal, set_str_signal) = signal("div > p.some-class");
use_element_size(str_signal);
}

Signals of Elements: Signal<web_sys::Element>, ReadSignal<web_sys::Element>, RwSignal<web_sys::Element>, Memo<web_sys::Element>; also works with Option<web_sys::Element> and SendWrapper<web_sys::Element>:

#![allow(unused)]
fn main() {
let (el_signal, set_el_signal) = signal(document().query_selector("div > p.some-class").unwrap());
use_element_size(el_signal);
}

How it works

Looking at the source code of use_element_size you'll find sth like

#![allow(unused)]
fn main() {
pub fn use_element_size(el: Into<ElementMaybeSignal<...>>) -> UseElementSizeReturn {}
}

All the above code works because there are From implementations for all of these types for ElementMaybeSignal.

ElementsMaybeSignal

Some functions work on one or more elements. Take use_resize_observer for example. This works very much the same way as described above but instead of Into<ElementMaybeSignal> it takes an Into<ElementsMaybeSignal> (note the plural). This means you can use it exactly in the same ways as you saw with the singular ElementMaybeSignal. Only this time, when you use String or &str it will be interpreted as CSS selector with query_selector_all.

But you can also use it with containers.

#![allow(unused)]
fn main() {
// Array of Option<web_sys::Element>
use_resize_observer([window().body(), document().query_selector("div > p.some-class").unsrap()]);

// Vec of &str. All of them will be interpreted as CSS selectors with query_selector_all() and the
// results will be merged into one Vec.
use_resize_observer(vec!["div > p.some-class", "p.some-class"]);

// Slice of NodeRef
let node_ref1 = NodeRef::<Div>::new();
let node_ref2 = NodeRef::<Div>::new();
use_resize_observer(vec![node_ref1, node_ref2].as_slice());
}

Usage in Options

Some functions have options that take Element(s)MaybeSignal. They can be used in the same way.

#![allow(unused)]
fn main() {
use_mouse_with_options(
    UseMouseOptions::default().target("div > p.some-class")
);
}

See also "Excluding Elements" in on_click_outside.

Server-Side Rendering

When using together with server-side rendering (SSR) you have to enable the feature ssr similar to how you do it for leptos.

In your Cargo.toml file enable Leptos-Use's ssr feature only from your project's ssr feature:

[dependencies]
leptos-use = "0.10"   # do NOT enable the "ssr" feature here

...

[features]
hydrate = [
    "leptos/hydrate",
    ...
]
ssr = [
    ...
    "leptos/ssr",
    ...
    "leptos-use/ssr" # <== add this
]

...

Please see the ssr example in the examples folder for a simple working demonstration.

Many functions work differently on the server and on the client. If that's the case you will find information about these differences in their respective docs under the section "Server-Side Rendering". If you don't find that section, it means that the function works exactly the same on both, the client and the server.

Do not enable the ssr feature directly!

Don't do the following.

[dependencies]
leptos-use = { version = "0.10", features = ["ssr"] }  # this is wrong

The ssr feature is used to select which version of the functions are built. Effectively it means your application is built two times: with ssr enabled to build the server executable, and with ssr disabled to build the client's WASM binary module.

So if you enable leptos-use's ssr feature globally, you will get the server version of the functions in the client.

By adding "leptos-use/ssr" to the ssr feature of your project, it will only be enabled when your project is built with ssr, and you will get the server functions server-side, and the client functions client-side.

WASM on the server

If you enable ssr in your project on a wasm32 target architecture, you will get a compile-time warning in the console because it is a common mistake that users enable ssr globally. If you're using wasm32 on the server however you can safely disable this warning by enabling the wasm_ssr feature together with ssr.

Functions with Target Elements

A lot of functions like use_resize_observer and use_element_size are only useful when a target HTML/SVG element is available. This is not always the case on the server. If you use them with NodeRefs they will just work in SSR. But what if you want to use them with window() or document()?

To enable that we provide the helper functions use_window() and use_document() which return a new-type-wrapped Option<web_sys::Window> or Option<web_sys::Document> respectively. These can be used safely on the server. The following code works on both the client and the server:

#![allow(unused)]
fn main() {
use leptos::prelude::*;
use leptos::ev::keyup;
use leptos_use::{use_event_listener, use_window};

use_event_listener(use_window(), keyup, | evt| {
...
});
}

There are some convenience methods provided as well, like use_document().body() which just propagate a None on the server.

Encoding and Decoding Data

Several functions encode and decode data for storing it and/or sending it over the network. To do this, codecs from the crate codee are used. They implement the traits Encoder with the method encode and Decoder with the method decode.

There are two types of codecs: One that encodes as binary data (Vec[u8]) and another type that encodes as strings (String). There is also an adapter Base64 that can be used to wrap a binary codec and make it a string codec by representing the binary data as a base64 string.

Please check the documentation of codee for more details and a list of all available codecs.

Example

In this example, a codec is given to use_cookie that stores data as a string in the JSON format. Since cookies can only store strings, we have to use string codecs here.

use leptos::*;
use leptos_use::use_cookie;
use serde::{Deserialize, Serialize};
use codee::string::JsonCodec;

#[component]
pub fn App(cx: Scope) -> impl IntoView {
#[derive(Serialize, Deserialize, Clone)]
struct MyState {
    chicken_count: i32,
    egg_count: i32,
}

let (cookie, set_cookie) = use_cookie::<MyState, JsonCodec>("my-state-cookie");    
view! {}
}

Custom Codecs

If you don't find a suitable codec for your needs, you can implement your own; it's straightforward! If you want to create a string codec, you can look at JsonSerdeCodec. In case it's a binary codec, have a look at BincodeSerdeCodec.

Versioning

For a discussion on how to implement versioning please refer to the relevant section in the docs for codee.

Changelog

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

[0.16.3] - 2025-09-30

Change

• Implemented PartialEq for core::Position

Fixes 🍕

• Fixed effects running simultaneously in use_cookie (thanks to @ cbishopvelti)
• Fixed link to Leptos Getting Started in the book (thanks to @mbergkvist)
• Fixed SSR in use_interval_fn (thanks to @johansmitsnl)

Special thanks to our sponsor

• @benwis

[0.16.2] - 2025-06-18

Fixes 🍕

• use_color_mode frontend-only logic behind feature gate to fix SendWrapper issues with SSR (thanks to @BakerNet)

Special thanks to our sponsor

• @benwis

[0.16.1] - 2025-06-16

Dependency Fixes 🐛

• Removed version pin for chrono
• Made chrono optional in Cargo.toml (thanks to @emilbonnek)

Special thanks to our sponsor

• @benwis

[0.16.0] - 2025-06-12

Breaking Change 🛠

• Updated dependency Leptos to version 0.8.0 (thanks to @DerKnerd, @jaystile, @ifiokjr)

New Features 🚀

• Added month_by_date to use_calendar (thanks to @tomaszkubacki)
• Added target_offset to use_draggable (thanks to @theredfish)
• UseRwSignal can now be converted from anything that implements the respective reactive Leptos traits. This includes Signals, Memos, Store fields, ... meaning the sync_signal now works with everything.
• ElementMaybeSignal can be converted from Signal<SendWrapper<web_sys::Element>> improving interop with other crates.

Fixes 🍕

• use_cookie with SSR has been fixed. This fixes the use_color_mode SSR issues as well.
• use_event_source with infinity reconnect limit has been fixed.
• Conversion of ElementMaybeSignal from &str has been fixed.

Special thanks to our sponsor

• @benwis

[0.16.0-beta2] - 2025-03-20

Breaking Change 🛠

• Updated dependency Leptos to version 0.8.0 (thanks to @DerKnerd, @jaystile)

New Feature 🚀

• Added target_offset to use_draggable options for more flexible positioning (thanks to @theredfish)

Special thanks to our sponsors

• @benwis
• @spencewenski

[0.16.0-beta] - 2025-03-20

Breaking Change 🛠

• Updated dependency Leptos to version 0.8.0-beta (thanks to @ifiokjr)

New Feature 🚀

• Added month_by_date to use_calendar (thanks to @tomaszkubacki)

Special thanks to our sponsors

• @benwis
• @spencewenski

[0.16.0-alpha] - 2025-03-17

Breaking Changes 🛠

• Removed the feature spin and it's backend integration dependency leptos-spin (thanks to @ifiokjr)
• Updated dependency Leptos to version 0.8.0-alpha (thanks to @ifiokjr)
• Updated dependency getrandom to version 0.3
• Updated dependency rand to version 0.9

Special thanks to our sponsor

• @spencewenski

[0.15.8] - 2025-06-12

New Features 🚀

• Added month_by_date to use_calendar (thanks to @tomaszkubacki)
• Added target_offset to use_draggable (thanks to @theredfish)
• UseRwSignal can now be converted from anything that implements the respective reactive Leptos traits. This includes Signals, Memos, Store fields, ... meaning the sync_signal now works with everything.
• ElementMaybeSignal can be converted from Signal<SendWrapper<web_sys::Element>> improving interop with other crates.

Fixes 🍕

• use_cookie with SSR has been fixed. This fixes the use_color_mode SSR issues as well.
• use_event_source with infinity reconnect limit has been fixed.
• Conversion of ElementMaybeSignal from &str has been fixed.

Special thanks to our sponsor

• @benwis

[0.15.7] - 2025-03-17

Change

• Updated codee version to 0.3.0 in line with the latest 0.7 Leptos versions

Special thanks to our sponsor

• @spencewenski

[0.15.6] - 2025-02-08

Fix 🍕

• Fixed use_storage overwriting stored values with SSR (thanks to @BakerNet).

Special thanks to our sponsor

• @spencewenski

[0.15.5] - 2025-01-15

Fix 🍕

• sync_signal with immediate = true now syncs the signals on the server once initially. This fixes use_color_mode with cookies enabled to give wrong results during SSR.

Special thanks to our sponsor

• @spencewenski

[0.15.4] - 2025-01-15

Fixes 🍕

• downgraded codee to 0.2.0 to be compatible with Leptos 0.7
• fixed use_mutation_observer (thanks to @bpwarner)

Changes 🔥

• improxed DX: implemented Clone + Copy for UseDropZoneReturn (thanks to @mahmoud-eltahawy)

Special thanks to our sponsor

• @spencewenski

[0.15.3] - 2025-01-08 (yanked)

New Function 🚀

• use_calendar

Fix 🍕

• added Debug to Size (thanks to @Ahlman)

Special thanks to our sponsor

• @spencewenski

[0.15.2] - 2025-01-03

Fixes 🍕

• Fixed path of use_color_mode cookie
• ElementMaybeSignal and ElementsMaybeSignal are now properly Clone and Copy

Special thanks to our sponsor

• @spencewenski

[0.15.1] - 2024-12-31

Fixes 🍕

• Fixed use_element_hover not properly cancelling it's timeout (thanks to @jcold).
• Fixed use_storage not writing default values.
• Fixed unidirectional sync_signal not syncing properly.

Special thanks to our sponsors

• @spencewenski
• LeftClick

[0.15.0] - 2024-12-17

New Functions 🚀

• signal_throttled and signal_debounced now have ..._local variants (thanks to @bicarlsen)

Breaking Changes 🛠

• use_storage now accepts a Signal as it's key parameter (thanks to LeftClick)
• use_websocket now supports sending heartbeats (thanks to LeftClick)

Fix 🍕

• Fixed use_storage to actually remove the key when remove is called (thanks to @flaviopezzini)

Special thanks to our sponsors

• @spencewenski
• LeftClick

[0.14.0] - 2024-12-01

Highlights since 0.13

• Updated to Leptos 0.7
• Refactored ElementMaybeSignal and ElementsMaybeSignal to have a simpler implementation. For the vast majority of cases this should continue to work as before.
• Almost everything returned from functions is now Send + Sync.

Changes since 0.14.0-rc5

• Updated Leptos to use stable 0.7 version
• Updated wasm-bindgen to 0.2.96
• Updated web-sys 0.3.73

Special thanks to our sponsor:

• @spencewenski

[0.14.0-rc5] - 2024-11-27

• fixed error messages for get_header
• added Send + Sync to storage return closure

Special thanks to our sponsor:

• @spencewenski

[0.14.0-rc4] - 2024-11-26

• Updated to Leptos 0.7.0-rc2
• Fixed WASM on the serverside (thanks to @GuillaumeDelorme)
• Fixed use_storage.
• Made all returned closures Send + Sync.

Special thanks to our sponsor:

• @spencewenski

[0.14.0-rc3] - 2024-11-14

• Fixed potential SSR panic in use_locale(s) (thanks to @veigaribo)
• Make use_locale prioritize user preferred locales over app preferred ones

[0.14.0-rc2] - 2024-11-10

• Updated to Leptos 0.7.0-rc1
• Updated to web-sys 0.3.72 and unpinned version (thanks to @sabify)
• Added dependabot (thanks to @sabify)
• Reverted use_user_media to have video enabled by default
• Fixed exponential increase on websocket reconnects

[0.14.0-rc1] - 2024-11-06

• Fixed MediaTrackConstraints dependency (thanks to @mollymorphous)
• Fixed warnings and tests (thanks to @SleeplessOne1917 and @jheuel)
• Unpinned the wasm-bindgen version (thanks to @jheuel)

[0.14.0-rc0] - 2024-11-03

• Latest changes up to version 0.13.7 ported
• Updated to Leptos 0.7.0-rc0

[0.14.0-gamma2] - 2024-10-16

• Updated to Leptos 0.7.0-gamma3 by using Signal instead of MaybeSignal

[0.14.0-gamma1] - 2024-10-10

• Adapted to the latest changes in Leptos (thanks to @BakerNet and @nikessel)
• Fixed all the examples
• use_active_element ported
• use_drop_zone now returns Signal<Vec<SendSignal<web_sys::File>>> instead of Signal<Vec<web_sys::File>, LocalStorage> to make it easier to use with <For>

[0.14.0-beta4] - 2024-09-15

• Latest changes from version 0.13.4 and 0.13.5 ported

[0.14.0-beta3] - 2024-09-02

Breaking Changes 🛠

• Refactored ElementMaybeSignal and ElementsMaybeSignal to have a simpler implementation. For the vast majority of cases this should continue to work as before.

[0.14.0-beta2] - 2024-09-09

Change 🔥

• Latest Leptos 0.7 beta changed the trigger trait method (thanks to @BakerNet)
• Latest changes from version 0.13.3 ported

[0.14.0-beta1] - 2024-09-02

Ported everything to Leptos 0.7 Some example don't run yet.

[0.13.12] - 2025-01-03

• Fixed path of use_color_mode cookie

Thanks to our generous sponsor:

• @spencewenski

[0.13.11] - 2024-11-22

• Updated web-sys version to 0.3.72

Thanks to our generous sponsor:

• @spencewenski

[0.13.10] - 2024-11-14

• Fixed potential SSR crash in use_locale(s) (thanks to @veigaribo)

[0.13.9] - 2024-11-10

• Reverted use_user_media to have video enabled by default
• Fixed exponential increase on websocket reconnects

[0.13.8] - 2024-11-06

• Backported fixes from 0.14.0-rc1

[0.13.7] - 2024-10-20

• Added video and audio options to use_user_media (thanks to @sauloco).
• Fixed cookies in SSR (thanks to @jim-taylor-business).

[0.13.6] - 2024-10-20

• Updated leptos-spin version to 0.2 (thanks to @tqq1994516).

[0.13.5] - 2024-09-15

New Function 🚀

• use_textarea_autosize

[0.13.4] - 2024-09-05

Fix 🍕

• use_websocket now returns a signal for the websocket instance so the user can actually use it. Before it always returned None.

[0.13.3] - 2024-09-02

Fix 🍕

• Fixed use_color_mode with cookies enabled

[0.13.2] - 2024-09-02

Fix 🍕

• Fixed web-sys unstable_apis flag for use_web_lock

[0.13.1] - 2024-09-01

New Functions 🚀

• use_web_lock
• use_window_size

Change 🔥

• UseWebsocket::protocols now supports a signal. It is read right before open is called. (thanks to @zakstucke)

[0.13.0] - 2024-08-28

New Functions 🚀

• use_toggle
• use_prefers_reduced_motion (thanks to @hcandelaria)

Breaking Changes 🛠

• use_websocket now supports different types for sending and receiving messages
• SyncSignalOptions now can take now either transformations or assignment functions but not both.
• updated to codee version 0.2.0

Fixes 🍕

• use_websocket fixed error with cleanup and reconnect (thanks to @BakerNet).

New Features 🚀

• There is now a feature for almost every function to get better compile and rust-analyzer times.
• use_web_notification now supports the vibrate option (thanks to @hcandelaria).
• UseDocument now supports a whole bunch of methods more from document (thanks to @luckynumberke7in).

[0.12.0] - 2024-08-14

Make sure you also update cargo-leptos to the latest version if you use that.

Breaking Changes 🛠

• Updated to web_sys 0.3.70 which unfortunately is breaking some things.
• use_clipboard doesn't need the unstable flags anymore.
• use_locale now uses unic_langid::LanguageIdentifier and proper locale matching (thanks to @mondeja).
• Removed UseMouseEventExtractorDefault and reworked UseMouseCoordType (thanks to @carloskiki)
• use_preferred_dark and use_color_mode now try to read the Sec-CH-Prefers-Color-Scheme header in SSR. This brings the necessity to enable an additional feature for them (axum / actix / spin).

Fixes 🍕

• Fixed the codec chapter in the book to refer to crate codee.

[0.11.4] - 2024-08-12

New Features 🚀

• use_web_notification now supports the options renotify, silent and image (thanks to @hcandelaria).
• sync_signal no supports the options assign_ltr and assign_rtl.

[0.11.3] - 2024-07-31

Fix 🍕

• Made use_timeout_fn SSR-safe

[0.11.2] - 2024-07-30

Change 🔥

• use_locale has now a supported locale list.

(yanked) [0.11.1] - 2024-07-28

New Functions 🚀

• use_locale (thanks to @BrandonDyer64)
• use_locales (thanks to @BrandonDyer64)
• header – Standard implementations for reading a header on the server.

[0.11.0] - 2024-07-27

New Functions 🚀

• use_user_media

New Features 🚀

• Codecs:

  • All codecs now live in their own crate codee
  • There are now binary codecs in addition to string codecs.
    • FromToBytesCodec
    • WebpackSerdeCodec
    • BincodeSerdeCodec
    • ProstCodec (see also the section "Breaking Changes 🛠" below)
  • Every binary codec can be used as a string codec with the Base64 wrapper which encodes the binary data as a base64 string.
    • This required feature base64
    • It can be wrapped for example like this: Base64<WebpackSerdeCodec>.
  • There is now an OptionCodec wrapper that allows to wrap any string codec that encodes T to encode Option<T>.
    • Use it like this: OptionCodec<FromToStringCodec<f64>>.

• ElementMaybeSignal is now implemented for websys::HtmlElement (thanks to @blorbb).

• UseStorageOptions now has delay_during_hydration which has to be used when you conditionally show parts of the DOM controlled by a value from storage. This leads to hydration errors which can be fixed by setting this new option to true.

• cookie::SameSite is now re-exported

• Changing the signal returned by use_cookie now tries and changes the headers during SSR.

• New book chapter about codecs

• The macro use_derive_signal! is now exported (thanks to @mscofield0).

Breaking Changes 🛠

• UseStorageOptions and UseEventSourceOptions no longer accept a codec value because this is already provided as a generic parameter to the respective function calls.
• Codecs have been refactored. There are now two traits that codecs implement: Encoder and Decoder. The trait StringCodec is gone. The methods are now associated methods and their params now always take references.
  • JsonCodec has been renamed to JsonSerdeCodec.
  • The feature to enable this codec is now called json_serde instead of just serde.
  • ProstCodec now encodes as binary data. If you want to keep using it with string data you can wrap it like this: Base64<ProstCodec>.
  • All of these structs, traits and features now live in their own crate called codee
  • A bunch of new codecs are available. Have a look at the docs for crate codee.
• use_websocket:
  • UseWebsocketOptions has been renamed to UseWebSocketOptions (uppercase S) to be consistent with the return type.
  • UseWebSocketOptions::reconnect_limit and UseEventSourceOptions::reconnect_limit is now ReconnectLimit instead of u64. Use ReconnectLimit::Infinite for infinite retries or ReconnectLimit::Limited(...) for limited retries.
  • use_websocket now uses codecs to send typed messages over the network.
    • When calling you have give type parameters for the message type and the codec: use_websocket::<String, WebpackSerdeCodec>
    • You can use binary or string codecs.
    • The UseWebSocketReturn::send closure now takes a &T which is encoded using the codec.
    • The UseWebSocketReturn::message signal now returns an Option<T> which is decoded using the codec.
    • UseWebSocketReturn::send_bytes and UseWebSocketReturn::message_bytes are gone.
    • UseWebSocketOptions::on_message and UseWebSocketOptions::on_message_bytes have been renamed to on_message_raw and on_message_raw_bytes.
    • The new UseWebSocketOptions::on_message takes a &T.
    • UseWebSocketOptions::on_error now takes a UseWebSocketError instead of a web_sys::Event.
• use_storage now always saves the default value to storage if the key doesn't exist yet.
• Renamed BreakpointsSematic to BreakpointsSemantic and breakpoints_sematic to breakpoints_semantic (note the n) (thanks to @mondeja).

Fixes 🍕

• Fixed auto-reconnect in use_websocket
• Fixed typo in compiler error messages in use_cookie (thanks to @SleeplessOne1917).
• Fixed potential signal out of scope issue with use_raf_fn

Other Changes 🔥

• Better links in docs that work both in the book and in rustdoc (thanks to @mondeja).
• Better CI/CD (thanks to @EstebanBorai).

[0.10.10] - 2024-05-10

Change 🔥

• Added compile-time warning when you use ssr feature with wasm32. You can enable wasm_ssr to remove the warning.

[0.10.9] - 2024-04-27

Fixes 🍕

• Fixed use_color_mode without cookies and make cookies sync properly with local storage
• Fixed use_infinite_scroll edge case bug with disposed signals

[0.10.8] - 2024-04-19

Change 🔥

• use_cookie now supports Spin out of the box (thanks to @javierEd).

[0.10.7] - 2024-04-10

New Function 🚀

• sync_signal

Change 🔥

• use_color_mode now supports cookies.

[0.10.6] - 2024-04-02

Fixes 🍕

• Corrected docs of use_cookie's max-age unit to milliseconds (thanks to @sify21).
• Fixed setting multiple cookies in the browser (thanks to @sbking).

[0.10.5] - 2024-03-12

Fix 🍕

• Fixed SSR detection from an url query parameter for use_color_mode (thanks to @mondeja).

[0.10.4] - 2024-03-05

New Functions 🚀

• use_event_source

Changes 🔥

• Wrapped callbacks in a non-reactive zone to remove potential warnings.
• Updated SSR chapter in the book to make it more clear and beginner-friendly (thanks to @flupke).

[0.10.3] - 2024-02-23

New Functions 🚀

• use_or
• use_and
• use_not

Fix 🍕

• Removed signal warnings from use_websocket's send... methods.

Changes 🔥

• use_color_mode now supports detection from an url query parameter. (thanks to @mondeja)

[0.10.2] - 2024-02-09

New Functions 🚀

• use_permission
• use_clipboard
• use_timeout_fn

[0.10.1] - 2024-01-31

Fix 🍕

• Fixed docs.rs build

[0.10.0] - 2024-01-31

New Functions 🚀

• use_broadcast_channel
• use_cookie (thanks to @rakshith-ravi)
• use_mouse_in_element
• use_device_orientation (thanks to @mondeja)
• use_device_pixel_ratio (thanks to @mondeja)
• use_element_bounding

Breaking Changes 🛠

• The leptos version is now 0.6
• The trait Codec has been renamed to StringCodec and has been moved to util::StringCodec.
  • The struct StringCodec has been renamed to FromToStringCodec and has been moved to util::FromToStringCodec.
  • The structs JsonCodec and ProstCodec have been moved to util as well.
• The function use_storage now requires type parameters for the stored type and the codec like all the other ...storage... functions.

Fixes 🍕

• Fixed use_geolocation SSR compile issue
• Fixed use_intl_number_format maximum fraction digits option

Changes 🔥

• The UseMouseReturn signals x, y, and source_type are now of type Signal<f64> instead of ReadSignal<f64>.
• You can now convert leptos::html::HtmlElement<T> into Element(s)MaybeSignal. This should make functions a lot easier to use in directives.
• There's now a chapter in the book especially for Element(s)MaybeSignal.
• Throttled or debounced callbacks (in watch__ or __fn) no longer are called after the containing scope was cleaned up.
• The document returned from use_document now supports the methods query_selector and query_selector_all.

[0.9.0] - 2023-12-06

New Functions 🚀

• use_display_media (thanks to @seanaye)

Breaking Changes 🛠

• (@feral-dot-io) The use use_<type>_storage functions have been rewritten to use Codecs instead of always requiring serde.
  • This also removes the feature storage
  • By default the StringCodec is used which relies on types implementing FromString + ToString
  • If you want to use JsonCodec you have to enable the feature serde
  • If you want to use ProstCodec (new!) you have to enable the feature prost.
• (@feral-dot-io) The Rust flag --cfg=web_sys_unstable_apis is not needed anymore since relevant web_sys APIs are now stable. This affects in particular
  • use_element_size
  • use_resize_observer

Fixes 🍕

• use_raf_fn and use_timestamp no longer spam warnings because of getting signals outside of reactive contexts.
• use_infinite_scroll no longer calls the callback twice for the same event
• use_scroll now uses try_get_untracked in the debounced callback to avoid panics if the context has been destroyed while the callback was waiting to be called.
• use_idle works properly now (no more idles too early).
• use_web_notification doesn't panic on the server anymore.

[0.8.2] - 2023-11-09

Fixes 🍕

• Fixed SSR for
  • use_timestamp
  • use_raf_fn
  • use_idle

[0.8.1] - 2023-10-28

Fixes 🍕

• Using strings for ElementMaybeSignal and ElementsMaybeSignal is now SSR safe.
  • This fixes specifically use_color_mode to work on the server.

[0.8.0] - 2023-10-24

New Functions 🚀

• use_web_notification (thanks to @centershocks44)
• use_infinite_scroll
• use_service_worker (thanks to @lpotthast)

Breaking Changes 🛠

• use_scroll returns impl Fn(T) + Clone instead of Box<dyn Fn(T)>.

Other Changes 🔥

• UseScrollReturn is now documented

[0.7.2] - 2023-10-21

Fixes 🍕

• Some functions still used window() which could lead to panics in SSR. This is now fixed. Specifically for use_draggable.

[0.7.1] - 2023-10-02

New Function 🚀

• use_sorted

[0.7.0] - 2023-09-30

New Functions 🚀

• use_timestamp
• use_idle
• use_document
• use_window
• use_geolocation
• signal_debounced
• signal_throttled

Breaking Changes 🛠

• Leptos version is now 0.5
• No cx: Scope params are supported/needed anymore because of the changes in Leptos. Please check the release notes of Leptos 0.5 for how to upgrade.
• watch is now deprecated in favor of leptos::watch and will be removed in a future release. watch_with_options will continue to exist.
• use_event_listener_with_options now takes a UseEventListenerOptions instead of a web_sys::AddEventListenerOptions.
• use_mutation_observer_with_options now takes a UseMutationObserverOptions instead of a web_sys::MutationObserverInit.
• use_websocket:
  • takes now a &str instead of a String as its url parameter.
  • same for the returned send method.
  • The ready_state return type is now renamed to ConnectionReadyState instead of UseWebSocketReadyState.
  • The returned signals ready_state, message, message_bytes have now the type Signal<...> instead of ReadSignal<...> to make them more consistent with other functions.
  • The options reconnect_limit and reconnect_interval now take a u64 instead of Option<u64> to improve DX.
  • The option manual has been renamed to immediate to make it more consistent with other functions. To port please note that immediate is the inverse of manual (immediate = !manual).
  • Added documentation how pass it ergonomically as context.
• use_color_mode:
  • The optional on_changed handler parameters have changed slightly. Please refer to the docs for more details.
• Throttled or debounced functions cannot be FnOnce anymore.
• All traits ClonableFn... have been removed.

Other Changes 🔥

• use_websocket can use relative urls now
• Callbacks in options don't require to be cloneable anymore
• Callback in use_raf_fn doesn't require to be cloneable anymore
• All (!) functions can now be safely called on the server. Specifically this includes the following that before panicked on the server:
  • use_scroll
  • use_event_listener
  • use_element_hover
  • on_click_outside
  • use_drop_zone
  • use_element_size
  • use_element_visibility
  • use_resize_observer
  • use_intersection_observer
  • use_mutation_observer

Fixes 🍕

• use_element_visibility didn't work in some cases on Chrome properly. This has been fixed.

[0.6.3] - 2023-08-12

Fixes 🍕

• use_websocket panicked after unmount

[0.6.2] - 2023-08-03

Fixes 🍕

• use_event_listener_with_options removes the handlers now correctly.

[0.6.1] - 2023-08-03

Fixes 🍕

• use_storage now uses .get_untracked() to avoid warnings.

[0.6.0] - 2023-07-17

New Functions 🚀

• use_draggable
• use_to_string
• is_err
• is_ok
• is_none
• is_some
• use_raf_fn

Breaking Changes 🛠

• The following functions now accept a MaybeRwSignal as their initial/default value which means you can use a synchronized RwSignal in those places.
  • use_color_mode
  • use_cycle_list
  • use_favicon
  • use_storage
  • use_local_storage
  • use_session_storage
• Instead of returning ReadSignal, the following functions now return Signal.
  • use_color_mode
  • use_favicon
  • use_storage
  • use_local_storage
  • use_session_storage

Fixes 🍕

• use_drop_zone now uses .get_untracked() in event handlers

[0.5.0] - 2023-07-15

New Functions 🚀

• use_drop_zone
• use_websocket (thanks @sectore)
• use_intl_number_format

Changes 🔥

• Crate is ready for Server-Side Rendering. Enable feature ssr like you do for leptos.

[0.4.1] - 2023-07-07

New Functions 🚀

• use_window_focus
• use_window_scroll
• use_document_visibility

[0.4.0] - 2023-07-03

Breaking Changes 🛠

• Required leptos version is now 0.4
• Following the changes in leptos there is no longer a stable crate feature required in order to use this library with a stable toolchain. If you want to use it with a nightly toolchain you have to enable the nightly feature only on leptos directly. No change is required for leptos-use itself.

[0.3.3] - 2023-06-24

New Functions 🚀

• use_color_mode
• use_cycle_list
• use_active_element

Changes 🔥

• You can now use this crate with the stable toolchain (thanks @lpotthast)
• Set leptos dependency to default-features = false in order to enable SSR.

[0.3.2] - 2023-06-17

New Functions 🚀

• use_css_var
• use_element_hover

[0.3.1] - 2023-06-15

New Functions 🚀

• use_interval_fn
• use_interval

[0.3.0] - 2023-06-13

Breaking Changes 🛠

• use_event_listener no longer returns a Box<dyn Fn()> but a impl Fn() + Clone

Changes 🔥

• You can now specify a &str or Signal<String> with CSS selectors wherever a node ref is accepted
• Callbacks of the following functions no longer require Clone
  • use_resize_observer
  • use_intersection_observer
• These functions now also accept multiple target elements in addition to a single one:
  • use_resize_observer
  • use_intersection_observer

New Functions 🚀

• whenever
• use_mutation_observer
• use_abs
• on_click_outside

[0.2.1] - 2023-06-11

New Functions

• use_intersection_observer
• use_element_visibility

[0.2.0] - 2023-06-11

Breaking Changes

• watch doesn't accept immediate as a direct argument anymore. This is only provided by the option variant.
• watch has now variant watch_with_options which allows for debouncing and throttling.

New Functions

• use_storage
• use_local_storage
• use_session_storage
• watch_debounced
• watch_throttled
• watch_pausable
• use_ceil
• use_round
• use_media_query
• use_preferred_dark
• use_preferred_contrast
• use_favicon
• use_breakpoints

Other Changes

• Function count badge in readme

[0.1.8/9] - 2023-06-05

• Fixed documentation and doc tests running for functions behind #[cfg(web_sys_unstable_apis)]

[0.1.7] - 2023-06-05

New Function

• use_element_size

[0.1.6] - 2023-06-03

Changes

• Fixed documentation so all feature are documented

[0.1.5] - 2023-06-03

New Functions

• use_floor
• use_max
• use_min

Changes

• New feature: math that has to be activated in order to use the math functions.

[0.1.4] - 2023-06-02

New Functions

• use_supported
• use_resize_observer
• watch
• use_mouse

Changes

• Use the crate default-struct-builder to provide ergonimic function options.

[0.1.3] - 2023-05-28

New Functions

• use_scroll
• use_debounce_fn

Other Changes

• Better and more beautiful demo integration into the guide.

Functions

Storage

• use_local_storage – Reactive LocalStorage.
• use_session_storage – Reactive SessionStorage.
• use_storage – Reactive Storage.

Elements

• use_active_element – Reactive document.activeElement
• use_document – SSR safe document().
• use_document_visibility – Reactively track document.visibilityState
• use_draggable – Make elements draggable.
• use_drop_zone – Create a zone where files can be dropped.
• use_element_bounding – Reactive bounding box of an HTML element
• use_element_size – Reactive size of an HTML element.
• use_element_visibility – Tracks the visibility of an element within the viewport.
• use_intersection_observer – Reactive IntersectionObserver.
• use_mouse_in_element – Reactive mouse position related to an element.
• use_mutation_observer – Reactive MutationObserver.
• use_resize_observer – Reports changes to the dimensions of an Element's content or the border-box.
• use_window – SSR safe window().
• use_window_focus – Reactively track window focus
• use_window_scroll – Reactive window scroll.
• use_window_size – Reactive window size.

Browser

• use_breakpoints – Reactive viewport breakpoints.
• use_broadcast_channel – Reactive BroadcastChannel API.
• use_clipboard – Reactive Clipboard API.
• use_color_mode – Reactive color mode (dark / light / customs) with auto data persistence.
• use_cookie – SSR-friendly and reactive cookie access.
• use_css_var – Manipulate CSS variables.
• use_display_media – Reactive mediaDevices.getDisplayMedia streaming.
• use_event_listener – Use EventListener with ease.
• use_favicon – Reactive favicon.
• use_media_query – Reactive Media Query.
• use_permission – Reactive Permissions API.
• use_preferred_contrast – Reactive prefers-contrast media query.
• use_preferred_dark – Reactive dark theme preference.
• use_prefers_reduced_motion – Reactive reduced motions preference.
• use_service_worker – Reactive ServiceWorker API.
• use_textarea_autosize – Automatically update the height of a textarea depending on the content.
• use_user_media – Reactive mediaDevices.getUserMedia streaming.
• use_web_lock – Rustified Web Locks API.
• use_web_notification – Reactive Notification API.

Intl

• use_intl_number_format – Reactive Intl.NumberFormat.
• use_locale – Reactive locale matching.
• use_locales – Reactive locales.

Sensors

• on_click_outside – Listen for clicks outside an element.
• use_device_orientation – Reactive DeviceOrientationEvent.
• use_device_pixel_ratio – Reactive window.devicePixelRatio
• use_element_hover – Reactive element's hover state.
• use_geolocation – Reactive Geolocation API.
• use_idle – Tracks whether the user is being inactive.
• use_infinite_scroll – Infinite scrolling of the element.
• use_mouse – Reactive mouse position
• use_scroll – We have to check if the scroll amount is close enough to some threshold in order to

Network

• use_event_source – Reactive EventSource
• use_websocket – Creating and managing a Websocket connection.

Animation

• use_interval – Reactive counter increases on every interval.
• use_interval_fn – Wrapper for set_interval with controls.
• use_raf_fn – Call function on every requestAnimationFrame.
• use_timeout_fn – Wrapper for setTimeout with controls.
• use_timestamp – Reactive current timestamp.

Watch

• watch_debounced – A debounced version of [watch].
• watch_pausable – Pausable [watch].
• watch_throttled – A throttled version of leptos::watch.
• watch_with_options – A version of leptos::watch but with additional options.
• whenever – Shorthand for watching a signal to be true.

Utilities

Math

• use_abs – Reactive abs().
• use_and – Reactive AND condition.
• use_ceil – Reactive ceil().
• use_floor – Reactive floor().
• use_max – Reactive max().
• use_min – Reactive min().
• use_not – Reactive NOT condition.
• use_or – Reactive OR condition.
• use_round – Reactive round().

use_local_storage

Reactive LocalStorage.

LocalStorage stores data in the browser with no expiration time. Access is given to all pages from the same origin (e.g., all pages from "https://example.com" share the same origin). While data doesn't expire the user can view, modify and delete all data stored. Browsers allow 5MB of data to be stored.

This is in contrast to use_session_storage which clears data when the page session ends and is not shared.

Usage

See use_storage for more details on how to use.

Feature

This function is only available if the crate feature storage is enabled

Source

Source • Docs

use_session_storage

Reactive SessionStorage.

SessionStorages stores data in the browser that is deleted when the page session ends. A page session ends when the browser closes the tab. Data is not shared between pages. While data doesn't expire the user can view, modify and delete all data stored. Browsers allow 5MB of data to be stored.

Use use_local_storage to store data that is shared amongst all pages with the same origin and persists between page sessions.

Usage

See use_storage for more details on how to use.

Feature

This function is only available if the crate feature storage is enabled

Source

Source • Docs

use_storage

Reactive Storage.

The function returns a triplet (read_signal, write_signal, delete_from_storage_fn).

Demo

Usage

Pass a StorageType to determine the kind of key-value browser storage to use. The specified key is where data is stored. All values are stored as UTF-16 strings which is then encoded and decoded via the given *Codec. This value is synced with other calls using the same key on the same page and across tabs for local storage. See UseStorageOptions to see how behavior can be further customised.

Values are (en)decoded via the given codec. You can use any of the string codecs or a binary codec wrapped in Base64.

Please check the codec chapter to see what codecs are available and what feature flags they require.

Example

use leptos::prelude::*;
use leptos_use::storage::{StorageType, use_local_storage, use_session_storage, use_storage};
use serde::{Deserialize, Serialize};
use codee::string::{FromToStringCodec, JsonSerdeCodec, Base64};
use codee::binary::ProstCodec;

#[component]
pub fn Demo() -> impl IntoView {
// Binds a struct:
let (state, set_state, _) = use_local_storage::<MyState, JsonSerdeCodec>("my-state");

// Binds a bool, stored as a string:
let (flag, set_flag, remove_flag) = use_session_storage::<bool, FromToStringCodec>("my-flag");

// Binds a number, stored as a string:
let (count, set_count, _) = use_session_storage::<i32, FromToStringCodec>("my-count");
// Binds a number, stored in JSON:
let (count, set_count, _) = use_session_storage::<i32, JsonSerdeCodec>("my-count-kept-in-js");

// Bind string with SessionStorage stored in ProtoBuf format:
let (id, set_id, _) = use_storage::<String, Base64<ProstCodec>>(
    StorageType::Session,
    "my-id",
);
   view! { }
}

// Data stored in JSON must implement Serialize, Deserialize.
// And you have to add the feature "serde" to your project's Cargo.toml
#[derive(Serialize, Deserialize, Clone, PartialEq)]
pub struct MyState {
    pub hello: String,
    pub greeting: String,
}

// Default can be used to implement initial or deleted values.
// You can also use a signal via UseStorageOptions::default_value`
impl Default for MyState {
    fn default() -> Self {
        Self {
            hello: "hi".to_string(),
            greeting: "Hello".to_string()
        }
    }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server the returned signals will just read/manipulate the initial_value without persistence.

Hydration bugs and use_cookie

If you use a value from storage to control conditional rendering you might run into issues with hydration.

use leptos::prelude::*;
use leptos_use::storage::use_session_storage;
use codee::string::FromToStringCodec;

#[component]
pub fn Example() -> impl IntoView {
let (flag, set_flag, _) = use_session_storage::<bool, FromToStringCodec>("my-flag");

view! {
    <Show when=move || flag.get()>
        <div>Some conditional content</div>
    </Show>
}
}

You can see hydration warnings in the browser console and the conditional parts of the app might never show up when rendered on the server and then hydrated in the browser. The reason for this is that the server has no access to storage and therefore will always use initial_value as described above. So on the server your app is always rendered as if the value from storage was initial_value. Then in the browser the actual stored value is used which might be different, hence during hydration the DOM looks different from the one rendered on the server which produces the hydration warnings.

The recommended way to avoid this is to use use_cookie instead because values stored in cookies are available on the server as well as in the browser.

If you still want to use storage instead of cookies you can use the delay_during_hydration option that will use the initial_value during hydration just as on the server and delay loading the value from storage by an animation frame. This gets rid of the hydration warnings and makes the app correctly render things. Some flickering might be unavoidable though.

use leptos::prelude::*;
use leptos_use::storage::{use_local_storage_with_options, UseStorageOptions};
use codee::string::FromToStringCodec;

#[component]
pub fn Example() -> impl IntoView {
let (flag, set_flag, _) = use_local_storage_with_options::<bool, FromToStringCodec>(
    "my-flag",
    UseStorageOptions::default().delay_during_hydration(true),
);

view! {
    <Show when=move || flag.get()>
        <div>Some conditional content</div>
    </Show>
}
}

Feature

This function is only available if the crate feature storage is enabled

Types

• enum UseStorageError
• struct UseStorageOptions

Source

Source • Demo • Docs

use_active_element

Reactive document.activeElement

Demo

Usage

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::use_active_element;

#[component]
fn Demo() -> impl IntoView {
let active_element = use_active_element();

Effect::new(move || {
    log!("focus changed to {:?}", active_element.get());
});

view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this returns a Signal that always contains the value None.

Feature

This function is only available if the crate feature use_active_element is enabled

Source

Source • Demo • Docs

use_document

SSR safe document(). This returns just a new-type wrapper around Option<Document>. Calling this amounts to None on the server and Some(Document) on the client.

It provides some convenient methods for working with the document like body().

Usage

use leptos::prelude::*;
use leptos_use::use_document;

#[component]
fn Demo() -> impl IntoView {
let document = use_document();

// Returns `None` on the server but will not panic.
let body = document.body();

view! { }
}

Feature

This function is only available if the crate feature use_document is enabled

Types

• struct UseDocument

Source

Source • Docs

use_document_visibility

Reactively track document.visibilityState

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_document_visibility;

#[component]
fn Demo() -> impl IntoView {
let visibility = use_document_visibility();

view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this returns a Signal that always contains the value web_sys::VisibilityState::Hidden.

Feature

This function is only available if the crate feature use_document_visibility is enabled

Source

Source • Demo • Docs

use_draggable

Make elements draggable.

Demo

Usage

use leptos::prelude::*;
use leptos::html::Div;
use leptos_use::{use_draggable_with_options, UseDraggableOptions, UseDraggableReturn};
use leptos_use::core::Position;

#[component]
fn Demo() -> impl IntoView {
let el = NodeRef::<Div>::new();

// `style` is a helper string "left: {x}px; top: {y}px;"
let UseDraggableReturn {
    x,
    y,
    style,
    ..
} = use_draggable_with_options(
    el,
    UseDraggableOptions::default().initial_value(Position { x: 40.0, y: 40.0 }),
);

view! {
    <div node_ref=el style=move || format!("position: fixed; {}", style.get())>
        Drag me! I am at { x }, { y }
    </div>
}
}

Feature

This function is only available if the crate feature use_draggable is enabled

Types

• struct UseDraggableOptions
• struct UseDraggableCallbackArgs
• struct UseDraggableReturn

Source

Source • Demo • Docs

use_drop_zone

Create a zone where files can be dropped.

Demo

Usage

use leptos::prelude::*;
use leptos::html::Div;
use leptos_use::{use_drop_zone_with_options, UseDropZoneOptions, UseDropZoneReturn};

#[component]
fn Demo() -> impl IntoView {
let drop_zone_el = NodeRef::<Div>::new();

let on_drop = |event| {
    // called when files are dropped on zone
};

let UseDropZoneReturn {
    is_over_drop_zone,
    ..
} = use_drop_zone_with_options(
    drop_zone_el,
    UseDropZoneOptions::default().on_drop(on_drop)
);

view! {
    <div node_ref=drop_zone_el>
        "Drop files here"
    </div>
}
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server the returned file signal always contains an empty Vec and is_over_drop_zone contains always false

Feature

This function is only available if the crate feature use_drop_zone is enabled

Types

• struct UseDropZoneOptions
• struct UseDropZoneEvent
• struct UseDropZoneReturn

Source

Source • Demo • Docs

use_element_bounding

Reactive bounding box of an HTML element

Demo

Usage

use leptos::prelude::*;
use leptos::html::Div;
use leptos_use::{use_element_bounding, UseElementBoundingReturn};

#[component]
fn Demo() -> impl IntoView {
let el = NodeRef::<Div>::new();
let UseElementBoundingReturn {
    x, y, top,right,bottom,left, width, height, ..
} = use_element_bounding(el);

view! { <div node_ref=el></div> }
}

SendWrapped Return

The returned closure update is a sendwrapped function. It can only be called from the same thread that called use_element_bounding.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server the returned signals always are 0.0 and update is a no-op.

Feature

This function is only available if the crate feature use_element_bounding is enabled

Types

• struct UseElementBoundingOptions
• struct UseElementBoundingReturn

Source

Source • Demo • Docs

use_element_size

Reactive size of an HTML element.

Please refer to ResizeObserver on MDN for more details.

Demo

Usage

use leptos::{html::Div, prelude::*};
use leptos_use::{use_element_size, UseElementSizeReturn};

#[component]
fn Demo() -> impl IntoView {
let el = NodeRef::<Div>::new();

let UseElementSizeReturn { width, height } = use_element_size(el);

view! {
    <div node_ref=el>
        "Width: " {width}
        "Height: " {height}
    </div>
}
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server the returned signals always contain the value of the initial_size option.

See also

• fn@crate::use_resize_observer

Feature

This function is only available if the crate feature use_element_size is enabled

Types

• struct UseElementSizeOptions
• struct UseElementSizeReturn

Source

Source • Demo • Docs

use_element_visibility

Tracks the visibility of an element within the viewport.

Demo

Usage

use leptos::prelude::*;
use leptos::html::Div;
use leptos_use::use_element_visibility;

#[component]
fn Demo() -> impl IntoView {
let el = NodeRef::<Div>::new();

let is_visible = use_element_visibility(el);

view! {
    <div node_ref=el>
        <h1>{is_visible}</h1>
    </div>
}
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this returns a Signal that always contains the value false.

See also

• fn@crate::use_intersection_observer

Feature

This function is only available if the crate feature use_element_visibility is enabled

Types

• struct UseElementVisibilityOptions

Source

Source • Demo • Docs

use_intersection_observer

Reactive IntersectionObserver.

Detects that a target element's visibility inside the viewport.

Demo

Usage

use leptos::prelude::*;
use leptos::html::Div;
use leptos_use::use_intersection_observer;

#[component]
fn Demo() -> impl IntoView {
let el = NodeRef::<Div>::new();
let (is_visible, set_visible) = signal(false);

use_intersection_observer(
    el,
    move |entries, _| {
        set_visible.set(entries[0].is_intersecting());
    },
);

view! {
    <div node_ref=el>
        <h1>"Hello World"</h1>
    </div>
}
}

SendWrapped Return

The returned closures pause, resume and stop are sendwrapped functions. They can only be called from the same thread that called use_intersection_observer.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this amounts to a no-op.

See also

• fn@crate::use_element_visibility

Feature

This function is only available if the crate feature use_intersection_observer is enabled

Types

• struct UseIntersectionObserverOptions
• struct UseIntersectionObserverReturn

Source

Source • Demo • Docs

use_mouse_in_element

Reactive mouse position related to an element.

Demo

Usage

use leptos::prelude::*;
use leptos::html::Div;
use leptos_use::{use_mouse_in_element, UseMouseInElementReturn};

#[component]
fn Demo() -> impl IntoView {
let target = NodeRef::<Div>::new();
let UseMouseInElementReturn { x, y, is_outside, .. } = use_mouse_in_element(target);

view! {
    <div node_ref=target>
        <h1>Hello world</h1>
    </div>
}
}

SendWrapped Return

The returned closure stop is a sendwrapped function. It can only be called from the same thread that called use_mouse_in_element.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this returns simple Signals with the initial_value for x and y, no-op for stop, is_outside = true and 0.0 for the rest of the signals.

Feature

This function is only available if the crate feature use_mouse_in_element is enabled

Types

• struct UseMouseInElementOptions
• struct UseMouseInElementReturn

Source

Source • Demo • Docs

use_mutation_observer

Reactive MutationObserver.

Watch for changes being made to the DOM tree.

Demo

Usage

use leptos::prelude::*;
use leptos::html::Pre;
use leptos_use::{use_mutation_observer_with_options, UseMutationObserverOptions};

#[component]
fn Demo() -> impl IntoView {
let el = NodeRef::<Pre>::new();
let (text, set_text) = signal("".to_string());

use_mutation_observer_with_options(
    el,
    move |mutations, _| {
        if let Some(mutation) = mutations.first() {
            set_text.update(|text| *text = format!("{text}\n{:?}", mutation.attribute_name()));
        }
    },
    UseMutationObserverOptions::default().attributes(true),
);

view! {
    <pre node_ref=el>{ text }</pre>
}
}

SendWrapped Return

The returned closure stop is a sendwrapped function. It can only be called from the same thread that called use_mouse_in_element.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this amounts to a no-op.

Feature

This function is only available if the crate feature use_mutation_observer is enabled

Types

• struct UseMutationObserverOptions
• struct UseMutationObserverReturn

Source

Source • Demo • Docs

use_resize_observer

Reports changes to the dimensions of an Element's content or the border-box.

Please refer to ResizeObserver on MDN for more details.

Demo

Usage

use leptos::{html::Div, prelude::*};
use leptos_use::use_resize_observer;

#[component]
fn Demo() -> impl IntoView {
let el = NodeRef::<Div>::new();
let (text, set_text) = signal("".to_string());

use_resize_observer(
    el,
    move |entries, observer| {
        let rect = entries[0].content_rect();
        set_text.set(format!("width: {}\nheight: {}", rect.width(), rect.height()));
    },
);

view! {
    <div node_ref=el>{ move || text.get() }</div>
}
}

SendWrapped Return

The returned closure stop is a sendwrapped function. It can only be called from the same thread that called use_resize_observer.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this amounts to a no-op.

See also

• fn@crate::use_element_size

Feature

This function is only available if the crate feature use_resize_observer is enabled

Types

• struct UseResizeObserverOptions
• struct UseResizeObserverReturn

Source

Source • Demo • Docs

use_window

SSR safe window(). This returns just a new-type wrapper around Option<Window>. Calling this amounts to None on the server and Some(Window) on the client.

It provides some convenient methods for working with the window like document() and navigator(). These will all return None on the server.

Usage

use leptos::prelude::*;
use leptos_use::use_window;

#[component]
fn Demo() -> impl IntoView {
let window = use_window();

// Returns `None` on the server but will not panic.
let navigator = window.navigator();

view! { }
}

Feature

This function is only available if the crate feature use_window is enabled

Types

• struct UseWindow

Source

Source • Docs

use_window_focus

Reactively track window focus with window.onfocus and window.onblur events.

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_window_focus;

#[component]
fn Demo() -> impl IntoView {
let focused = use_window_focus();

view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this returns a Signal that is always true.

Feature

This function is only available if the crate feature use_window_focus is enabled

Source

Source • Demo • Docs

use_window_scroll

Reactive window scroll.

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_window_scroll;

#[component]
fn Demo() -> impl IntoView {
let (x, y) = use_window_scroll();

view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this returns Signals that are always 0.0.

Feature

This function is only available if the crate feature use_window_scroll is enabled

Source

Source • Demo • Docs

use_window_size

Reactive window size.

Demo

Usage

use leptos::*;
use leptos_use::{use_window_size, UseWindowSizeReturn};

#[component]
fn Demo() -> impl IntoView {
let UseWindowSizeReturn { width, height } = use_window_size();

view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server the width and height are always initial_size which defaults to Size { width: INFINITY, height: INFINITY }.

Feature

This function is only available if the crate feature use_window_size is enabled

Types

• struct UseWindowSizeOptions
• enum MeasureType
• struct UseWindowSizeReturn

Source

Source • Demo • Docs

use_breakpoints

Reactive viewport breakpoints.

Demo

Usage

use leptos::prelude::*;
use leptos_use::{use_breakpoints, BreakpointsTailwind, breakpoints_tailwind};

#[component]
fn Demo() -> impl IntoView {

let screen_width = use_breakpoints(breakpoints_tailwind());

use BreakpointsTailwind::*;

let sm_and_larger = screen_width.ge(Sm);
let larger_than_sm = screen_width.gt(Sm);
let lg_and_smaller = screen_width.le(Lg);
let smaller_than_lg = screen_width.lt(Lg);

view! { }
}

Breakpoints

There are many predefined breakpoints for major UI frameworks. The following are provided.

• breakpoints_tailwind
• breakpoints_bootstrap_v5
• breakpoints_material
• breakpoints_ant_design
• breakpoints_quasar
• breakpoints_semantic
• breakpoints_master_css

You can also provide your own breakpoints.

use std::collections::HashMap;
use leptos::prelude::*;
use leptos_use::use_breakpoints;

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
enum MyBreakpoints {
    Tablet,
    Laptop,
    Desktop,
}

fn my_breakpoints() -> HashMap<MyBreakpoints, u32> {
    use MyBreakpoints::*;

    HashMap::from([
        (Tablet, 640),
        (Laptop, 1024),
        (Desktop, 1280),
    ])
}

#[component]
fn Demo() -> impl IntoView {
    let screen_width = use_breakpoints(my_breakpoints());

    use MyBreakpoints::*;

    let laptop = screen_width.between(Laptop, Desktop);

    view! { }
}

Non-reactive methods

For every reactive method there is also a non-reactive variant that is prefixed with is_

use leptos::prelude::*;
use leptos_use::{use_breakpoints, BreakpointsTailwind, breakpoints_tailwind};

#[component]
fn Demo() -> impl IntoView {

let screen_width = use_breakpoints(breakpoints_tailwind());

use BreakpointsTailwind::*;

let sm_and_larger = screen_width.is_ge(Sm);
let larger_than_sm = screen_width.is_gt(Sm);
let lg_and_smaller = screen_width.is_le(Lg);
let smaller_than_lg = screen_width.is_lt(Lg);

view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

Since internally this uses fn@crate::use_media_query, which returns always false on the server, the returned methods also will return false.

Feature

This function is only available if the crate feature use_breakpoints is enabled

Types

• struct UseBreakpointsReturn
• enum BreakpointsTailwind
• enum BreakpointsBootstrapV5
• enum BreakpointsMaterial
• enum BreakpointsAntDesign
• enum BreakpointsQuasar
• enum BreakpointsSemantic
• enum BreakpointsMasterCss

Source

Source • Demo • Docs

use_broadcast_channel

Reactive BroadcastChannel API.

Closes a broadcast channel automatically when the component is cleaned up.

Demo

Usage

The BroadcastChannel interface represents a named channel that any browsing context of a given origin can subscribe to. It allows communication between different documents (in different windows, tabs, frames, or iframes) of the same origin.

Messages are broadcasted via a message event fired at all BroadcastChannel objects listening to the channel.

use leptos::prelude::*;
use leptos_use::{use_broadcast_channel, UseBroadcastChannelReturn};
use codee::string::FromToStringCodec;

#[component]
fn Demo() -> impl IntoView {
let UseBroadcastChannelReturn {
    is_supported,
    message,
    post,
    error,
    close,
    ..
} = use_broadcast_channel::<bool, FromToStringCodec>("some-channel-name");

post(&true);

close();

view! { }
}

Values are (en)decoded via the given codec. You can use any of the string codecs or a binary codec wrapped in Base64.

Please check the codec chapter to see what codecs are available and what feature flags they require.

use leptos::prelude::*;
use serde::{Deserialize, Serialize};
use leptos_use::use_broadcast_channel;
use codee::string::JsonSerdeCodec;

// Data sent in JSON must implement Serialize, Deserialize:
#[derive(Serialize, Deserialize, Clone, PartialEq)]
pub struct MyState {
    pub playing_lego: bool,
    pub everything_is_awesome: String,
}

#[component]
fn Demo() -> impl IntoView {
use_broadcast_channel::<MyState, JsonSerdeCodec>("everyting-is-awesome");
view! { }
}

SendWrapped Return

The returned closures post and close are sendwrapped functions. They can only be called from the same thread that called use_broadcast_channel.

Feature

This function is only available if the crate feature use_broadcast_channel is enabled

Types

• struct UseBroadcastChannelReturn
• enum UseBroadcastChannelError

Source

Source • Demo • Docs

use_clipboard

Reactive Clipboard API.

Provides the ability to respond to clipboard commands (cut, copy, and paste) as well as to asynchronously read from and write to the system clipboard. Access to the contents of the clipboard is gated behind the Permissions API. Without user permission, reading or altering the clipboard contents is not permitted.

Demo

Usage

use leptos::prelude::*;
use leptos_use::{use_clipboard, UseClipboardReturn};

#[component]
fn Demo() -> impl IntoView {
let UseClipboardReturn { is_supported, text, copied, copy } = use_clipboard();

view! {
    <Show
        when=move || is_supported.get()
        fallback=move || view! { <p>Your browser does not support Clipboard API</p> }
    >
        <button on:click={
            let copy = copy.clone();
            move |_| copy("Hello!")
        }>
            <Show when=move || copied.get() fallback=move || "Copy">
                "Copied!"
            </Show>
        </button>
    </Show>
}
}

SendWrapped Return

The returned closures copy is a sendwrapped function. It can only be called from the same thread that called use_clipboard.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server the returnd text signal will always be None and copy is a no-op.

Feature

This function is only available if the crate feature use_clipboard is enabled

Types

• struct UseClipboardOptions
• struct UseClipboardReturn

Source

Source • Demo • Docs

use_color_mode

Reactive color mode (dark / light / customs) with auto data persistence.

Demo

Usage

use leptos::prelude::*;
use leptos_use::{use_color_mode, UseColorModeReturn};

#[component]
fn Demo() -> impl IntoView {
let UseColorModeReturn {
    mode, // Signal<ColorMode::dark | ColorMode::light>
    set_mode,
    ..
} = use_color_mode();

view! { }
}

By default, it will match with users' browser preference using fn@crate::use_preferred_dark (a.k.a. ColorMode::Auto). When reading the signal, it will by default return the current color mode (ColorMode::Dark, ColorMode::Light or your custom modes ColorMode::Custom("some-custom")). The ColorMode::Auto variant can be included in the returned modes by enabling the emit_auto option and using use_color_mode_with_options. When writing to the signal (set_mode), it will trigger DOM updates and persist the color mode to local storage (or your custom storage). You can pass ColorMode::Auto to set back to auto mode.

use leptos::prelude::*;
use leptos_use::{ColorMode, use_color_mode, UseColorModeReturn};

#[component]
fn Demo() -> impl IntoView {
let UseColorModeReturn { mode, set_mode, .. } = use_color_mode();

mode.get(); // ColorMode::Dark or ColorMode::Light

set_mode.set(ColorMode::Dark); // change to dark mode and persist

set_mode.set(ColorMode::Auto); // change to auto mode

view! { }
}

Options

use leptos::prelude::*;
use leptos_use::{use_color_mode_with_options, UseColorModeOptions, UseColorModeReturn};

#[component]
fn Demo() -> impl IntoView {
let UseColorModeReturn { mode, set_mode, .. } = use_color_mode_with_options(
    UseColorModeOptions::default()
        .attribute("theme") // instead of writing to `class`
        .custom_modes(vec![
            // custom colors in addition to light/dark
            "dim".to_string(),
            "cafe".to_string(),
        ]),
); // Signal<ColorMode::Dark | ColorMode::Light | ColorMode::Custom("dim") | ColorMode::Custom("cafe")>

view! { }
}

Cookie

To persist color mode in a cookie, use use_cookie_with_options and specify .cookie_enabled(true).

Note: To work with SSR you have to add the axum or actix feature as described in fn@crate::use_cookie.

use leptos::prelude::*;
use leptos_meta::*;
use leptos_use::{use_color_mode_with_options, UseColorModeOptions, UseColorModeReturn};

#[component]
fn Demo() -> impl IntoView {
let UseColorModeReturn { mode, set_mode, .. } = use_color_mode_with_options(
    UseColorModeOptions::default()
        .cookie_enabled(true),
);

// This adds the color mode class to the `<html>` element even with SSR
view! {
    <Html {..} class=move || mode.get().to_string()/>
}
}

For a working example please check out the ssr example.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this will try to read the Sec-CH-Prefers-Color-Scheme header to determine the color mode. If the header is not present it will return ColorMode::Light. Please have a look at the linked documentation above for that header to see browser support as well as potential server requirements.

If you're using axum you have to enable the "axum" feature in your Cargo.toml. In case it's actix-web enable the feature "actix".

Bring your own header

In case you're neither using Axum nor Actix or the default implementation is not to your liking, you can provide your own way of reading the color scheme header value using the option crate::UseColorModeOptions::ssr_color_header_getter.

Cookie

If cookie_enabled is set to true, a cookie will be used and if present this value will be used on the server as well as on the client. Please note that you have to add the axum or actix feature as described in fn@crate::use_cookie.

See also

• fn@crate::use_preferred_dark
• fn@crate::storage::use_storage
• fn@crate::use_cookie

Feature

This function is only available if the crate feature use_color_mode is enabled

Types

• enum ColorMode
• struct UseColorModeOptions
• struct UseColorModeReturn

Source

Source • Demo • Docs

use_cookie

SSR-friendly and reactive cookie access.

You can use this function multiple times for the same cookie and their signals will synchronize (even across windows/tabs). But there is no way to listen to changes to document.cookie directly so in case something outside of this function changes the cookie, the signal will not be updated.

When the options max_age or expire is given then the returned signal will automatically turn to None after that time.

Demo

Usage

The example below creates a cookie called counter. If the cookie doesn't exist, it is initially set to a random value. Whenever we update the counter variable, the cookie will be updated accordingly.

use leptos::prelude::*;
use leptos_use::use_cookie;
use codee::string::FromToStringCodec;
use rand::random;


#[component]
fn Demo() -> impl IntoView {
let (counter, set_counter) = use_cookie::<u32, FromToStringCodec>("counter");

let reset = move || set_counter.set(Some(random()));

if counter.get().is_none() {
    reset();
}

let increase = move || {
    set_counter.set(counter.get().map(|c| c + 1));
};

view! {
    <p>Counter: {move || counter.get().map(|c| c.to_string()).unwrap_or("—".to_string())}</p>
    <button on:click=move |_| reset()>Reset</button>
    <button on:click=move |_| increase()>+</button>
}
}

Values are (en)decoded via the given codec. You can use any of the string codecs or a binary codec wrapped in Base64.

Please check the codec chapter to see what codecs are available and what feature flags they require.

Cookie attributes

As part of the options when you use use_cookie_with_options you can specify cookie attributes.

use cookie::SameSite;
use leptos::prelude::*;
use leptos_use::{use_cookie_with_options, UseCookieOptions};
use codee::string::FromToStringCodec;

#[component]
fn Demo() -> impl IntoView {
let (cookie, set_cookie) = use_cookie_with_options::<bool, FromToStringCodec>(
    "user_info",
    UseCookieOptions::default()
        .max_age(3600_000) // one hour
        .same_site(SameSite::Lax)
);

view! {}
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

This works equally well on the server or the client. On the server this function reads the cookie from the HTTP request header and writes it back into the HTTP response header according to options (if provided). The returned WriteSignal may not affect the cookie headers on the server! It will try and write the headers but if this happens after the headers have already been streamed to the client then this will have no effect.

If you're using axum you have to enable the "axum" feature in your Cargo.toml. In case it's actix-web enable the feature "actix"..

Bring your own header

In case you're neither using Axum nor Actix or the default implementation is not to your liking, you can provide your own way of reading and writing the cookie header value.

use cookie::Cookie;
use leptos::prelude::*;
use serde::{Deserialize, Serialize};
use leptos_use::{use_cookie_with_options, UseCookieOptions};
use codee::string::JsonSerdeCodec;

#[derive(Serialize, Deserialize, Clone, Debug, PartialEq)]
pub struct Auth {
    pub username: String,
    pub token: String,
}

#[component]
fn Demo() -> impl IntoView {
use_cookie_with_options::<Auth, JsonSerdeCodec>(
    "auth",
    UseCookieOptions::default()
        .ssr_cookies_header_getter(|| {
            #[cfg(feature = "ssr")]
            {
                Some("Somehow get the value of the cookie header as a string".to_owned())
            }
            #[cfg(not(feature = "ssr"))]
            None
        })
        .ssr_set_cookie(|cookie: &Cookie| {
            #[cfg(feature = "ssr")]
            {
                // somehow insert the Set-Cookie header for this cookie
            }
        }),
);
view! {}
}

Feature

This function is only available if the crate feature use_cookie is enabled

Types

• struct UseCookieOptions

Source

Source • Demo • Docs

use_css_var

Manipulate CSS variables.

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_css_var;

#[component]
fn Demo() -> impl IntoView {
let (color, set_color) = use_css_var("--color");

set_color.set("red".to_string());

view! { }
}

The variable name itself can be a Signal.

use leptos::prelude::*;
use leptos_use::use_css_var;

#[component]
fn Demo() -> impl IntoView {
let (key, set_key) = signal("--color".to_string());
let (color, set_color) = use_css_var(key);

view! { }
}

You can specify the element that the variable is applied to as well as an initial value in case the variable is not set yet. The option to listen for changes to the variable is also available.

use leptos::prelude::*;
use leptos::html::Div;
use leptos_use::{use_css_var_with_options, UseCssVarOptions};

#[component]
fn Demo() -> impl IntoView {
let el = NodeRef::<Div>::new();

let (color, set_color) = use_css_var_with_options(
    "--color",
    UseCssVarOptions::default()
        .target(el)
        .initial_value("#eee")
        .observe(true),
);

view! {
    <div node_ref=el>"..."</div>
}
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this simply returns signal(options.initial_value).

Feature

This function is only available if the crate feature use_css_var is enabled

Types

• struct UseCssVarOptions

Source

Source • Demo • Docs

use_display_media

Reactive mediaDevices.getDisplayMedia streaming.

Demo

Usage

use leptos::prelude::*;
use leptos::logging::{log, error};
use leptos_use::{use_display_media, UseDisplayMediaReturn};

#[component]
fn Demo() -> impl IntoView {
let video_ref = NodeRef::<leptos::html::Video>::new();

let UseDisplayMediaReturn { stream, start, .. } = use_display_media();

start();

Effect::new(move |_|
    video_ref.get().map(|v| {
        match stream.get() {
            Some(Ok(s)) => v.set_src_object(Some(&s)),
            Some(Err(e)) => error!("Failed to get media stream: {:?}", e),
            None => log!("No stream yet"),
        }
    })
);

view! { <video node_ref=video_ref controls=false autoplay=true muted=true></video> }
}

SendWrapped Return

The returned closures start and stop are sendwrapped functions. They can only be called from the same thread that called use_display_media.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server calls to start or any other way to enable the stream will be ignored and the stream will always be None.

Feature

This function is only available if the crate feature use_display_media is enabled

Types

• struct UseDisplayMediaOptions
• struct UseDisplayMediaReturn

Source

Source • Demo • Docs

use_event_listener

Use EventListener with ease.

Register using addEventListener on mounted, and removeEventListener automatically on cleanup.

Usage

use leptos::prelude::*;
use leptos::ev::visibilitychange;
use leptos::logging::log;
use leptos_use::{use_document, use_event_listener};

#[component]
fn Demo() -> impl IntoView {
use_event_listener(use_document(), visibilitychange, |evt| {
    log!("{:?}", evt);
});
   view! { }
}

You can also pass a NodeRef as the event target, use_event_listener will unregister the previous event and register the new one when you change the target.

use leptos::prelude::*;
use leptos::ev::click;
use leptos::logging::log;
use leptos_use::use_event_listener;

#[component]
fn Demo() -> impl IntoView {
let element = NodeRef::new();

use_event_listener(element, click, |evt| {
    log!("click from element {:?}", event_target::<web_sys::HtmlDivElement>(&evt));
});

let (cond, set_cond) = signal(true);

view! {
    <Show
        when=move || cond.get()
        fallback=move || view! { <div node_ref=element>"Condition false"</div> }
    >
        <div node_ref=element>"Condition true"</div>
    </Show>
}
}

You can also call the returned to unregister the listener.

use leptos::prelude::*;
use leptos::ev::keydown;
use leptos::logging::log;
use web_sys::KeyboardEvent;
use leptos_use::use_event_listener;

#[component]
fn Demo() -> impl IntoView {
let cleanup = use_event_listener(document().body(), keydown, |evt: KeyboardEvent| {
    log!("{}", &evt.key());
});

cleanup();

   view! { }
}

SendWrapped Return

The returned closure is a sendwrapped function. It can only be called from the same thread that called use_event_listener.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this amounts to a noop.

Feature

This function is only available if the crate feature use_event_listener is enabled

Types

• struct UseEventListenerOptions

Source

Source • Demo • Docs

use_favicon

Reactive favicon.

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_favicon;

#[component]
fn Demo() -> impl IntoView {

let (icon, set_icon) = use_favicon();

set_icon.set(Some("dark.png".to_string())); // change current icon

   view! { }
}

Passing a Source Signal

You can pass a Signal to use_favicon_with_options. Change from the source signal will be reflected in your favicon automatically.

use leptos::prelude::*;
use leptos_use::{use_favicon_with_options, UseFaviconOptions, use_preferred_dark};

#[component]
fn Demo() -> impl IntoView {

let is_dark = use_preferred_dark();

let (icon, _) = use_favicon_with_options(
    UseFaviconOptions::default().new_icon(
        Signal::derive(move || {
            Some((if is_dark.get() { "dark.png" } else { "light.png" }).to_string())
        }),
    )
);

   view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server only the signals work but no favicon will be changed obviously.

Feature

This function is only available if the crate feature use_favicon is enabled

Types

• struct UseFaviconOptions

Source

Source • Demo • Docs

use_media_query

Reactive Media Query.

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_media_query;

#[component]
fn Demo() -> impl IntoView {

let is_large_screen = use_media_query("(min-width: 1024px)");

let is_dark_preferred = use_media_query("(prefers-color-scheme: dark)");

   view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this functions returns a Signal that is always false.

See also

• fn@crate::use_preferred_dark
• fn@crate::use_preferred_contrast
• fn@crate::use_prefers_reduced_motion

Feature

This function is only available if the crate feature use_media_query is enabled

Source

Source • Demo • Docs

use_permission

Reactive Permissions API.

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_permission;

#[component]
fn Demo() -> impl IntoView {
let microphone_access = use_permission("microphone");

view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server the returned signal will always be PermissionState::Unknown.

Feature

This function is only available if the crate feature use_permission is enabled

Types

• enum PermissionState

Source

Source • Demo • Docs

use_preferred_contrast

Reactive prefers-contrast media query.

Usage

use leptos::prelude::*;
use leptos_use::use_preferred_contrast;

#[component]
fn Demo() -> impl IntoView {

let preferred_contrast = use_preferred_contrast();

   view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this returns a Signal that always contains the value PreferredContrast::NoPreference.

See also

• fn@crate::use_media_query
• fn@crate::use_preferred_dark
• fn@crate::use_prefers_reduced_motion

Feature

This function is only available if the crate feature use_preferred_contrast is enabled

Types

• enum PreferredContrast

Source

Source • Docs

use_preferred_dark

Reactive dark theme preference.

Usage

use leptos::prelude::*;
use leptos_use::use_preferred_dark;

#[component]
fn Demo() -> impl IntoView {

let is_dark_preferred = use_preferred_dark();

   view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this will try to read the Sec-CH-Prefers-Color-Scheme header to determine the color mode. If the header is not present it will return ColorMode::Light. Please have a look at the linked documentation above for that header to see browser support as well as potential server requirements.

If you're using axum you have to enable the "axum" feature in your Cargo.toml. In case it's actix-web enable the feature "actix".

Bring your own header

In case you're neither using Axum nor Actix or the default implementation is not to your liking, you can provide your own way of reading the color scheme header value using the option crate::UsePreferredDarkOptions::ssr_color_header_getter.

See also

• fn@crate::use_media_query
• fn@crate::use_preferred_contrast
• fn@crate::use_prefers_reduced_motion

Feature

This function is only available if the crate feature use_preferred_dark is enabled

Types

• struct UsePreferredDarkOptions

Source

Source • Docs

use_prefers_reduced_motion

Reactive reduced motions preference.

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_prefers_reduced_motion;
#[cfg(feature = "docs")]
use leptos_use::docs::BooleanDisplay;

#[component]
fn Demo() -> impl IntoView {
let is_reduced_motion_preferred = use_prefers_reduced_motion();

view! {
    <div>
        <p>Prefers reduced motions: <BooleanDisplay value=is_reduced_motion_preferred/></p>
        <p>
            Update reduce motion preference
            <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-reduced-motion#user_preferences">
                documentation.
            </a>
        </p>
    </div>
}
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this will try to read the Sec-CH-Prefers-Reduced-Motion header to indicate the preference for animations to be displayed with reduced motion. Please have a look at the linked documentation above to see browser support as well as potential serve requirements.

If you're using axum you have to enable the "axum" feature in your Cargo.toml. In case it's actix-web enable the feature "actix".

Bring your own header

In case you're neither using Axum nor Actix or the default implementation is not to your liking, you can provide your own way of reading the reduced motion header value using the option crate::UsePrefersReducedMotionOptions::ssr_motion_header_getter.

See also

• fn@crate::use_media_query
• fn@crate::use_preferred_contrast
• fn@crate::use_preferred_dark

Feature

This function is only available if the crate feature use_prefers_reduced_motion is enabled

Types

• struct UsePrefersReducedMotionOptions

Source

Source • Demo • Docs

use_service_worker

Reactive ServiceWorker API.

Please check the working example.

Usage

use leptos::prelude::*;
use leptos_use::{use_service_worker_with_options, UseServiceWorkerOptions, UseServiceWorkerReturn};

#[component]
fn Demo() -> impl IntoView {
let UseServiceWorkerReturn {
        registration,
        installing,
        waiting,
        active,
        skip_waiting,
        check_for_update,
} = use_service_worker_with_options(UseServiceWorkerOptions::default()
    .script_url("service-worker.js")
    .skip_waiting_message("skipWaiting"),
);

view! { }
}

SendWrapped Return

The returned closures check_for_update and skip_waiting are sendwrapped functions. They can only be called from the same thread that called use_service_worker.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

This function does not support SSR. Call it inside a create_effect.

Feature

This function is only available if the crate feature use_service_worker is enabled

Types

• struct UseServiceWorkerOptions
• struct UseServiceWorkerReturn
• enum ServiceWorkerRegistrationError

Source

Source • Demo • Docs

use_textarea_autosize

Automatically update the height of a textarea depending on the content.

Demo

Usage

Simple example

use leptos::prelude::*;
use leptos::html::Textarea;
use leptos_use::{use_textarea_autosize, UseTextareaAutosizeReturn};

#[component]
fn Demo() -> impl IntoView {
let textarea = NodeRef::new();

let UseTextareaAutosizeReturn {
    content,
    set_content,
    trigger_resize
} = use_textarea_autosize(textarea);

view! {
    <textarea
        prop:value=content
        on:input=move |evt| set_content.set(event_target_value(&evt))
        node_ref=textarea
        class="resize-none"
        placeholder="What's on your mind?"
    />
}
}

Make sure that you set box-sizing: border-box on the textarea element.

It's also recommended to reset the scrollbar styles for the textarea element to avoid incorrect height values for large amounts of text.

textarea {
  -ms-overflow-style: none;
  scrollbar-width: none;
}

textarea::-webkit-scrollbar {
  display: none;
}

With rows attribute

If you need support for the rows attribute on a textarea element, then you should set the style_prop option to "min-height".

use leptos::prelude::*;
use leptos::html::Textarea;
use leptos_use::{use_textarea_autosize_with_options, UseTextareaAutosizeOptions, UseTextareaAutosizeReturn};

#[component]
fn Demo() -> impl IntoView {
let textarea = NodeRef::new();

let UseTextareaAutosizeReturn {
    content,
    set_content,
    ..
} = use_textarea_autosize_with_options(
    textarea,
    UseTextareaAutosizeOptions::default().style_prop("min-height"),
);

view! {
    <textarea
        prop:value=content
        on:input=move |evt| set_content.set(event_target_value(&evt))
        node_ref=textarea
        class="resize-none"
        placeholder="What's on your mind?"
        rows="3"
    />
}
}

SendWrapped Return

The returned closure trigger_resize is a sendwrapped function. It can only be called from the same thread that called use_textarea_autosize.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this will always return an empty string as ´contentand a no-optrigger_resize`.

Feature

This function is only available if the crate feature use_textarea_autosize is enabled

Types

• struct UseTextareaAutosizeOptions
• struct UseTextareaAutosizeReturn

Source

Source • Demo • Docs

use_user_media

Reactive mediaDevices.getUserMedia streaming.

Demo

Usage

use leptos::prelude::*;
use leptos::logging::{log, error};
use leptos_use::{use_user_media, UseUserMediaReturn};

#[component]
fn Demo() -> impl IntoView {
let video_ref = NodeRef::<leptos::html::Video>::new();

let UseUserMediaReturn { stream, start, .. } = use_user_media();

start();

Effect::new(move |_|
    video_ref.get().map(|v| {
        match stream.get() {
            Some(Ok(s)) => v.set_src_object(Some(&s)),
            Some(Err(e)) => error!("Failed to get media stream: {:?}", e),
            None => log!("No stream yet"),
        }
    })
);

view! { <video node_ref=video_ref controls=false autoplay=true muted=true></video> }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server calls to start or any other way to enable the stream will be ignored and the stream will always be None.

Feature

This function is only available if the crate feature use_user_media is enabled

Types

• struct UseUserMediaOptions
• struct UseUserMediaReturn
• enum ConstraintExactIdeal
• enum ConstraintRange
• enum FacingMode
• enum AudioConstraints
• enum VideoConstraints
• struct VecMarker
• struct AudioTrackConstraints
• struct VideoTrackConstraints

Source

Source • Demo • Docs

use_web_lock

Rustified Web Locks API.

The Web Locks API allows scripts running in one tab or worker to asynchronously acquire a lock, hold it while work is performed, then release it. While held, no other script executing in the same origin can acquire the same lock, which allows a web app running in multiple tabs or workers to coordinate work and the use of resources.

This function requires --cfg=web_sys_unstable_apis to be activated as described in the wasm-bindgen guide.

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_web_lock;

async fn my_process(_lock: web_sys::Lock) -> i32 {
    // do sth
    42
}

#[component]
fn Demo() -> impl IntoView {
leptos::task::spawn_local(async {
    let res = use_web_lock("my_lock", my_process).await;
    assert!(matches!(res, Ok(42)));
});

view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this returns Err(UseWebLockError::Server) and the task is not executed.

Feature

This function is only available if the crate feature use_web_lock is enabled

Types

• enum UseWebLockError
• struct UseWebLockOptions

Source

Source • Demo • Docs

use_web_notification

Reactive Notification API.

The Web Notification interface of the Notifications API is used to configure and display desktop notifications to the user.

Demo

Usage

use leptos::prelude::*;
use leptos_use::{use_web_notification_with_options, UseWebNotificationOptions, ShowOptions, UseWebNotificationReturn, NotificationDirection};

#[component]
fn Demo() -> impl IntoView {
let UseWebNotificationReturn {
    show,
    close,
    ..
} = use_web_notification_with_options(
    UseWebNotificationOptions::default()
        .direction(NotificationDirection::Auto)
        .language("en")
        .renotify(true)
        .tag("test"),
);

show(ShowOptions::default().title("Hello World from leptos-use"));

view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

This function is basically ignored on the server. You can safely call show but it will do nothing.

Feature

This function is only available if the crate feature use_web_notification is enabled

Types

• enum NotificationDirection
• struct UseWebNotificationOptions
• struct ShowOptions
• enum NotificationPermission
• struct UseWebNotificationReturn

Source

Source • Demo • Docs

on_click_outside

Listen for clicks outside an element. Useful for modals or dropdowns.

Demo

Usage

use leptos::prelude::*;
use leptos::logging::log;
use leptos::html::Div;
use leptos_use::on_click_outside;

#[component]
fn Demo() -> impl IntoView {
let target = NodeRef::<Div>::new();

on_click_outside(target, move |event| { log!("{:?}", event); });

view! {
    <div node_ref=target>"Hello World"</div>
    <div>"Outside element"</div>
}
}

This function uses Event.composedPath() which is not supported by IE 11, Edge 18 and below. If you are targeting these browsers, we recommend you to include this code snippet on your project.

SendWrapped Return

The return value of this function is a sendwrapped function to remove all event listeners. It can only be called from the same thread that called on_click_outside.

Excluding Elements

Use this to ignore clicks on certain elements.

use leptos::prelude::*;
use leptos::logging::log;
use leptos::html::Div;
use leptos_use::{on_click_outside_with_options, OnClickOutsideOptions};

#[component]
fn Demo() -> impl IntoView {
let target = NodeRef::<Div>::new();

on_click_outside_with_options(
    target,
    move |event| { log!("{:?}", event); },
    OnClickOutsideOptions::default().ignore(["input", "#some-id"]),
);

view! {
    <div node_ref=target>"Hello World"</div>
}
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this amounts to a no-op.

Feature

This function is only available if the crate feature on_click_outside is enabled

Types

• struct OnClickOutsideOptions

Source

Source • Demo • Docs

use_device_orientation

Reactive DeviceOrientationEvent.

Provide web developers with information from the physical orientation of the device running the web page.

Demo

Usage

use leptos::prelude::*;
use leptos_use::{use_device_orientation, UseDeviceOrientationReturn};

#[component]
fn Demo() -> impl IntoView {
let UseDeviceOrientationReturn {
    is_supported,
    absolute,
    alpha,
    beta,
    gamma,
} = use_device_orientation();

view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this function returns values as if the orientation capabilties were not supported by the device.

Feature

This function is only available if the crate feature use_device_orientation is enabled

Types

• struct UseDeviceOrientationReturn

Source

Source • Demo • Docs

use_device_pixel_ratio

Reactive window.devicePixelRatio

NOTE: there is no event listener for window.devicePixelRatio change. So this function uses the same mechanism as described in this example.

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_device_pixel_ratio;

#[component]
fn Demo() -> impl IntoView {
let pixel_ratio = use_device_pixel_ratio();

view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this function returns a Signal that is always 1.0.

Feature

This function is only available if the crate feature use_device_pixel_ratio is enabled

Source

Source • Demo • Docs

use_element_hover

Reactive element's hover state.

Demo

Usage

use leptos::prelude::*;
use leptos::html::Button;
use leptos_use::use_element_hover;

#[component]
fn Demo() -> impl IntoView {
let el = NodeRef::<Button>::new();
let is_hovered = use_element_hover(el);

view! {
    <button node_ref=el>{ move || format!("{:?}", is_hovered.get()) }</button>
}
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this returns a Signal that always contains the value false.

Feature

This function is only available if the crate feature use_element_hover is enabled

Types

• struct UseElementHoverOptions

Source

Source • Demo • Docs

use_geolocation

Reactive Geolocation API.

It allows the user to provide their location to web applications if they so desire. For privacy reasons, the user is asked for permission to report location information.

Demo

Usage

use leptos::prelude::*;
use leptos_use::{use_geolocation, UseGeolocationReturn};

#[component]
fn Demo() -> impl IntoView {
let UseGeolocationReturn {
    coords,
    located_at,
    error,
    resume,
    pause,
} = use_geolocation();

view! { }
}

SendWrapped Return

The returned closures pause and resume are sendwrapped functions. They can only be called from the same thread that called use_geolocation.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server all signals returns will always contain None and the functions do nothing.

Feature

This function is only available if the crate feature use_geolocation is enabled

Types

• struct UseGeolocationOptions
• struct UseGeolocationReturn

Source

Source • Demo • Docs

use_idle

Tracks whether the user is being inactive.

Demo

Usage

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::{use_idle, UseIdleReturn};

#[component]
fn Demo() -> impl IntoView {
let UseIdleReturn {
    idle, last_active, ..
} = use_idle(5 * 60 * 1000); // 5 minutes

log!("{}", idle.get()); // true or false

view! { }
}

Programatically resetting:

use std::time::Duration;
use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::{use_idle, UseIdleReturn};

#[component]
fn Demo() -> impl IntoView {
let UseIdleReturn {
    idle, last_active, reset
} = use_idle(5 * 60 * 1000); // 5 minutes

reset(); // restarts the idle timer. Does not change the `last_active` value.

view! { }
}

SendWrapped Return

The returned closure reset is a sendwrapped function. It can only be called from the same thread that called use_idle.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this will always return static signals

UseIdleReturn{
    idle: Signal(initial_state),
    last_active: Signal(now),
    reset: || {}
}

Feature

This function is only available if the crate feature use_idle is enabled

Types

• struct UseIdleOptions
• struct UseIdleReturn

Source

Source • Demo • Docs

use_infinite_scroll

Infinite scrolling of the element.

Demo

Usage

use leptos::prelude::*;
use leptos::html::Div;
use leptos_use::{use_infinite_scroll_with_options, UseInfiniteScrollOptions};

#[component]
fn Demo() -> impl IntoView {
let el = NodeRef::<Div>::new();

let (data, set_data) = signal(vec![1, 2, 3, 4, 5, 6]);

let _ = use_infinite_scroll_with_options(
    el,
    move |_| async move {
        let len = data.with(|d| d.len());
        set_data.update(|data| *data = (1..len+6).collect());
    },
    UseInfiniteScrollOptions::default().distance(10.0),
);

view! {
    <div node_ref=el>
        <For each=move || data.get() key=|i| *i let:item>{ item }</For>
    </div>
}
}

The returned signal is true while new data is being loaded.

Feature

This function is only available if the crate feature use_infinite_scroll is enabled

Types

• struct UseInfiniteScrollOptions
• struct ScrollState

Source

Source • Demo • Docs

use_mouse

Reactive mouse position

Demo

Basic Usage

use leptos::prelude::*;
use leptos_use::{use_mouse, UseMouseReturn};

#[component]
fn Demo() -> impl IntoView {
let UseMouseReturn {
    x, y, source_type, ..
} = use_mouse();
view! { }
}

Touch is enabled by default. To only detect mouse changes, set touch to false. The dragover event is used to track mouse position while dragging.

use leptos::prelude::*;
use leptos_use::{use_mouse_with_options, UseMouseOptions, UseMouseReturn};

#[component]
fn Demo() -> impl IntoView {
let UseMouseReturn {
    x, y, ..
} = use_mouse_with_options(
    UseMouseOptions::default().touch(false)
);
view! { }
}

Custom Extractor

It's also possible to provide a custom extractor to get the position from the events.

use leptos::prelude::*;
use leptos::html::Div;
use web_sys::MouseEvent;
use leptos_use::{use_mouse_with_options, UseMouseOptions, UseMouseReturn, UseMouseEventExtractor, UseMouseCoordType};

#[derive(Clone)]
struct MyExtractor;

impl UseMouseEventExtractor for MyExtractor {
    fn extract_mouse_coords(&self, event: &MouseEvent) -> Option<(f64, f64)> {
        Some((event.offset_x() as f64, event.offset_y() as f64))
    }

    // don't implement fn extract_touch_coords to ignore touch events
}

#[component]
fn Demo() -> impl IntoView {
    let element = NodeRef::<Div>::new();

    let UseMouseReturn {
        x, y, source_type, ..
    } = use_mouse_with_options(
        UseMouseOptions::default()
            .target(element)
            .coord_type(UseMouseCoordType::Custom(MyExtractor))
    );
    view! { <div node_ref=element></div> }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this returns simple Signals with the initial_values.

Feature

This function is only available if the crate feature use_mouse is enabled

Types

• struct UseMouseOptions
• enum UseMouseCoordType
• struct UseMouseReturn
• enum UseMouseSourceType

Source

Source • Demo • Docs

use_scroll

We have to check if the scroll amount is close enough to some threshold in order to more accurately calculate arrivedState. This is because scrollTop/scrollLeft are non-rounded numbers, while scrollHeight/scrollWidth and clientHeight/clientWidth are rounded. https://developer.mozilla.org/en-US/docs/Web/API/Element/scrollHeight#determine_if_an_element_has_been_totally_scrolled

Feature

This function is only available if the crate feature use_scroll is enabled

Types

• struct UseScrollOptions
• enum ScrollBehavior
• struct UseScrollReturn
• struct ScrollOffset

Source

Source • Demo • Docs

use_event_source

Reactive EventSource

An EventSource or Server-Sent-Events instance opens a persistent connection to an HTTP server, which sends events in text/event-stream format.

Usage

Values are decoded via the given decoder. You can use any of the string codecs or a binary codec wrapped in Base64.

Please check the codec chapter to see what codecs are available and what feature flags they require.

use leptos::prelude::*;
use leptos_use::{use_event_source, UseEventSourceReturn};
use codee::string::JsonSerdeCodec;
use serde::{Deserialize, Serialize};

#[derive(Serialize, Deserialize, Clone, PartialEq)]
pub struct EventSourceData {
    pub message: String,
    pub priority: u8,
}

#[component]
fn Demo() -> impl IntoView {
let UseEventSourceReturn {
    ready_state, data, error, close, ..
} = use_event_source::<EventSourceData, JsonSerdeCodec>("https://event-source-url");

view! { }
}

Named Events

You can define named events when using use_event_source_with_options.

use leptos::prelude::*;
use leptos_use::{use_event_source_with_options, UseEventSourceReturn, UseEventSourceOptions};
use codee::string::FromToStringCodec;

#[component]
fn Demo() -> impl IntoView {
let UseEventSourceReturn {
    ready_state, data, error, close, ..
} = use_event_source_with_options::<String, FromToStringCodec>(
    "https://event-source-url",
    UseEventSourceOptions::default()
        .named_events(["notice".to_string(), "update".to_string()])
);

view! { }
}

Immediate

Auto-connect (enabled by default).

This will call open() automatically for you, and you don't need to call it by yourself.

Auto-Reconnection

Reconnect on errors automatically (enabled by default).

You can control the number of reconnection attempts by setting reconnect_limit and the interval between them by setting reconnect_interval.

use leptos::prelude::*;
use leptos_use::{use_event_source_with_options, UseEventSourceReturn, UseEventSourceOptions, ReconnectLimit};
use codee::string::FromToStringCodec;

#[component]
fn Demo() -> impl IntoView {
let UseEventSourceReturn {
    ready_state, data, error, close, ..
} = use_event_source_with_options::<bool, FromToStringCodec>(
    "https://event-source-url",
    UseEventSourceOptions::default()
        .reconnect_limit(ReconnectLimit::Limited(5))         // at most 5 attempts
        .reconnect_interval(2000)   // wait for 2 seconds between attempts
);

view! { }
}

SendWrapped Return

The returned closures open and close are sendwrapped functions. They can only be called from the same thread that called use_event_source.

To disable auto-reconnection, set reconnect_limit to 0.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server-side, use_event_source will always return ready_state as ConnectionReadyState::Closed, data, event and error will always be None, and open and close will do nothing.

Feature

This function is only available if the crate feature use_event_source is enabled

Types

• struct UseEventSourceOptions
• struct UseEventSourceReturn
• enum UseEventSourceError

Source

Source • Docs

use_websocket

Creating and managing a Websocket connection.

Demo

Usage

Values are (en)decoded via the given codec. You can use any of the codecs, string or binary.

Please check the codec chapter to see what codecs are available and what feature flags they require.

use leptos::prelude::*;
use codee::string::FromToStringCodec;
use leptos_use::{use_websocket, UseWebSocketReturn};
use leptos_use::core::ConnectionReadyState;

#[component]
fn Demo() -> impl IntoView {
let UseWebSocketReturn {
    ready_state,
    message,
    send,
    open,
    close,
    ..
} = use_websocket::<String, String, FromToStringCodec>("wss://echo.websocket.events/");

let send_message = move |_| {
    send(&"Hello, world!".to_string());
};

let status = move || ready_state.get().to_string();

let connected = move || ready_state.get() == ConnectionReadyState::Open;

let open_connection = move |_| {
    open();
};

let close_connection = move |_| {
    close();
};

view! {
    <div>
        <p>"status: " {status}</p>

        <button on:click=send_message disabled=move || !connected()>"Send"</button>
        <button on:click=open_connection disabled=connected>"Open"</button>
        <button on:click=close_connection disabled=move || !connected()>"Close"</button>

        <p>"Receive message: " {move || format!("{:?}", message.get())}</p>
    </div>
}
}

Here is another example using msgpack for encoding and decoding. This means that only binary messages can be sent or received. For this to work you have to enable the msgpack_serde feature flag.

use leptos::*;
use codee::binary::MsgpackSerdeCodec;
use leptos_use::{use_websocket, UseWebSocketReturn};
use serde::{Deserialize, Serialize};

#[component]
fn Demo() -> impl IntoView {
#[derive(Serialize, Deserialize)]
struct SomeData {
    name: String,
    count: i32,
}

let UseWebSocketReturn {
    message,
    send,
    ..
} = use_websocket::<SomeData, SomeData, MsgpackSerdeCodec>("wss://some.websocket.server/");

let send_data = move || {
    send(&SomeData {
        name: "John Doe".to_string(),
        count: 42,
    });
};

view! {}
}

Heartbeats

Heartbeats can be configured by the heartbeat option. You have to provide a heartbeat type, that implements the Default trait and an Encoder for it. This encoder doesn't have to be the same as the one used for the other websocket messages.

use leptos::*;
use codee::string::FromToStringCodec;
use leptos_use::{use_websocket_with_options, UseWebSocketOptions, UseWebSocketReturn};
use serde::{Deserialize, Serialize};

#[component]
fn Demo() -> impl IntoView {
#[derive(Default)]
struct Heartbeat;

// Simple example for usage with `FromToStringCodec`
impl std::fmt::Display for Heartbeat {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "<Heartbeat>")
    }
}

let UseWebSocketReturn {
    send,
    message,
    ..
} = use_websocket_with_options::<String, String, FromToStringCodec, _, _>(
    "wss://echo.websocket.events/",
    UseWebSocketOptions::default()
        // Enable heartbeats every 10 seconds. In this case we use the same codec as for the
        // other messages. But this is not necessary.
        .heartbeat::<Heartbeat, FromToStringCodec>(10_000),
);

view! {}
}

Relative Paths

If the provided url is relative, it will be resolved relative to the current page. Urls will be resolved like this the following. Please note that the protocol (http vs https) will be taken into account as well.

Usage with provide_context

The return value of use_websocket utilizes several type parameters which can make it cumbersome to use with provide_context + expect_context. The following example shows how to avoid type parameters with dynamic dispatch. This sacrifices a little bit of performance for the sake of ergonomics. However, compared to network transmission speeds this loss of performance is negligible.

First we define the struct that is going to be passed around as context.

use leptos::prelude::*;
use std::sync::Arc;

#[derive(Clone)]
pub struct WebsocketContext {
    pub message: Signal<Option<String>>,
    send: Arc<dyn Fn(&String)>,  // use Arc to make it easily cloneable
}

impl WebsocketContext {
    pub fn new(message: Signal<Option<String>>, send: Arc<dyn Fn(&String)>) -> Self {
        Self {
            message,
            send,
        }
    }

    // create a method to avoid having to use parantheses around the field
    #[inline(always)]
    pub fn send(&self, message: &str) {
        (self.send)(&message.to_string())
    }
}

Now you can provide the context like the following.

use leptos::prelude::*;
use codee::string::FromToStringCodec;
use leptos_use::{use_websocket, UseWebSocketReturn};
use std::sync::Arc;
#[derive(Clone)]
pub struct WebsocketContext {
    pub message: Signal<Option<String>>,
    send: Arc<dyn Fn(&String) + Send + Sync>,
}

impl WebsocketContext {
    pub fn new(message: Signal<Option<String>>, send: Arc<dyn Fn(&String) + Send + Sync>) -> Self {
        Self {
            message,
            send,
        }
    }
}

#[component]
fn Demo() -> impl IntoView {
let UseWebSocketReturn {
    message,
    send,
    ..
} = use_websocket::<String, String, FromToStringCodec>("ws:://some.websocket.io");

provide_context(WebsocketContext::new(message, Arc::new(send.clone())));

view! {}
}

Finally let's use the context:

use leptos::prelude::*;
use leptos_use::{use_websocket, UseWebSocketReturn};
use std::sync::Arc;
#[derive(Clone)]
pub struct WebsocketContext {
    pub message: Signal<Option<String>>,
    send: Arc<dyn Fn(&String)>,
}

impl WebsocketContext {
    #[inline(always)]
    pub fn send(&self, message: &str) {
        (self.send)(&message.to_string())
    }
}

#[component]
fn Demo() -> impl IntoView {
let websocket = expect_context::<WebsocketContext>();

websocket.send("Hello World!");

view! {}
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server the returned functions amount to no-ops.

Feature

This function is only available if the crate feature use_websocket is enabled

Types

• struct UseWebSocketOptions
• struct DummyEncoder
• struct HeartbeatOptions
• struct UseWebSocketReturn
• enum UseWebSocketError

Source

Source • Demo • Docs

use_interval

Reactive counter increases on every interval.

Demo

Usage

use leptos::prelude::*;
use leptos_use::{use_interval, UseIntervalReturn};

#[component]
fn Demo() -> impl IntoView {
let UseIntervalReturn {
    counter,
    reset,
    is_active,
    pause,
    resume
}  = use_interval( 200 );
view! { }
}

SendWrapped Return

The returned closures pause, resume and reset are sendwrapped functions. They can only be called from the same thread that called use_intersection_observer.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this function will simply be ignored.

Feature

This function is only available if the crate feature use_interval is enabled

Types

• struct UseIntervalOptions
• struct UseIntervalReturn

Source

Source • Demo • Docs

use_interval_fn

Wrapper for set_interval with controls.

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_interval_fn;
use leptos_use::utils::Pausable;

#[component]
fn Demo() -> impl IntoView {
let Pausable { pause, resume, is_active } = use_interval_fn(
    || {
        // do something
    },
    1000,
);
view! { }
}

SendWrapped Return

The returned closures pause and resume are sendwrapped functions. They can only be called from the same thread that called use_interval_fn.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this function will simply be ignored.

Feature

This function is only available if the crate feature use_interval_fn is enabled

Types

• struct UseIntervalFnOptions

Source

Source • Demo • Docs

use_raf_fn

Call function on every requestAnimationFrame. With controls of pausing and resuming.

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_raf_fn;
use leptos_use::utils::Pausable;

#[component]
fn Demo() -> impl IntoView {
let (count, set_count) = signal(0);

let Pausable { pause, resume, is_active } = use_raf_fn(move |_| {
    set_count.update(|count| *count += 1);
});

view! { <div>Count: { count }</div> }
}

You can use use_raf_fn_with_options and set immediate to false. In that case you have to call resume() before the callback is executed.

SendWrapped Return

The returned closures pause and resume are sendwrapped functions. They can only be called from the same thread that called use_interval_fn.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this does basically nothing. The provided closure will never be called.

Feature

This function is only available if the crate feature use_raf_fn is enabled

Types

• struct UseRafFnOptions
• struct UseRafFnCallbackArgs

Source

Source • Demo • Docs

use_timeout_fn

Wrapper for setTimeout with controls.

Demo

Usage

use leptos::prelude::*;
use leptos_use::{use_timeout_fn, UseTimeoutFnReturn};

#[component]
fn Demo() -> impl IntoView {
let UseTimeoutFnReturn { start, stop, is_pending, .. } = use_timeout_fn(
    |i: i32| {
        // do sth
    },
    3000.0
);

start(3);

view! { }
}

SendWrapped Return

The returned closures start and stop are sendwrapped functions. They can only be called from the same thread that called use_timeout_fn.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server the callback will never be run. The returned functions are all no-ops and is_pending will always be false.

Feature

This function is only available if the crate feature use_timeout_fn is enabled

Types

• struct UseTimeoutFnReturn

Source

Source • Demo • Docs

use_timestamp

Reactive current timestamp.

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_timestamp;

#[component]
fn Demo() -> impl IntoView {
let timestamp = use_timestamp();

view! { }
}

With controls:

use leptos::prelude::*;
use leptos_use::{use_timestamp_with_controls, UseTimestampReturn};

#[component]
fn Demo() -> impl IntoView {
let UseTimestampReturn {
    timestamp,
    is_active,
    pause,
    resume,
} = use_timestamp_with_controls();

view! { }
}

SendWrapped Return

The returned closures pause and resume of the ..._with_controls versions are sendwrapped functions. They can only be called from the same thread that called use_timestamp_with_controls.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this function will return a signal with the milliseconds since the Unix epoch. But the signal will never update (as there's no request_animation_frame on the server).

Feature

This function is only available if the crate feature use_timestamp is enabled

Types

• struct UseTimestampOptions
• enum TimestampInterval
• struct UseTimestampReturn

Source

Source • Demo • Docs

use_calendar

Create bare-bone calendar data to use in your component. See UseCalendarOptions for options and UseCalendarReturn for return values.

Demo

Usage

use leptos::prelude::*;
use leptos_use::{use_calendar, UseCalendarReturn};

#[component]
fn Demo() -> impl IntoView {
let UseCalendarReturn {
    dates,
    weekdays,
    previous_month,
    today,
    month_by_date,
    next_month
} = use_calendar();

view! {
}
}

Use use_calendar_with_options to change the initial date and first day of the week.

use leptos::prelude::*;
use chrono::NaiveDate;
use leptos_use::{use_calendar_with_options, UseCalendarReturn, UseCalendarOptions};

#[component]
fn Demo() -> impl IntoView {
let initial_date = RwSignal::new(
    Some(NaiveDate::from_ymd_opt(2022, 1, 1).unwrap())
);

let options = UseCalendarOptions::default()
    .first_day_of_the_week(6)
    .initial_date(initial_date);

let UseCalendarReturn {
    dates,
    weekdays,
    previous_month,
    today,
    month_by_date,
    next_month
} = use_calendar_with_options(options);

view! {
}
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

Not tested yet.

Feature

This function is only available if the crate feature use_calendar is enabled

Types

• struct UseCalendarOptions
• struct UseCalendarReturn
• enum CalendarDate

Source

Source • Demo • Docs

watch_debounced

A debounced version of watch.

Demo

Usage

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::watch_debounced;

pub fn Demo() -> impl IntoView {
    let (source, set_source) = signal(0);

watch_debounced(
    move || source.get(),
    move |_, _, _| {
        log!("changed!");
    },
    500.0,
);

   view! { }
}

This really is only shorthand shorthand for watch_with_options(deps, callback, WatchOptions::default().debounce(ms)).

Please note that if the current component is cleaned up before the debounced callback is called, the debounced callback will not be called.

There's also watch_debounced_with_options where you can specify the other watch options (except filter).

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::{watch_debounced_with_options, WatchDebouncedOptions};

pub fn Demo() -> impl IntoView {
    let (source, set_source) = signal(0);

watch_debounced_with_options(
    move || source.get(),
    move |_, _, _| {
        log!("changed!");
    },
    500.0,
    WatchDebouncedOptions::default().max_wait(Some(1000.0)),
);

   view! { }
}

Recommended Reading

• Debounce vs Throttle: Definitive Visual Guide
• Debouncing and Throttling Explained Through Examples

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server the callback will never be called except if you set immediate to true in which case the callback will be called exactly once.

See also

• leptos::watch
• fn@crate::watch_throttled

Feature

This function is only available if the crate feature watch_debounced is enabled

Types

• struct WatchDebouncedOptions

Source

Source • Demo • Docs

watch_pausable

Pausable watch.

Demo

Usage

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::{watch_pausable, WatchPausableReturn};

pub fn Demo() -> impl IntoView {
let (source, set_source) = signal("foo".to_string());

let WatchPausableReturn {
    stop,
    pause,
    resume,
    ..
} = watch_pausable(
    move || source.get(),
    |v, _, _| {
        log!("Changed to {}", v);
    },
);

set_source.set("bar".to_string()); // > "Changed to bar"

pause();

set_source.set("foobar".to_string()); // (nothing happens)

resume();

set_source.set("hello".to_string()); // > "Changed to hello"
   view! { }
}

There's also watch_pausable_with_options which takes the same options as watch.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this works just fine except if you throttle or debounce in which case the callback will never be called except if you set immediate to true in which case the callback will be called exactly once.

See also

• leptos::watch

Feature

This function is only available if the crate feature watch_pausable is enabled

Types

• struct WatchPausableReturn

Source

Source • Demo • Docs

watch_throttled

A throttled version of leptos::watch.

Demo

Usage

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::watch_throttled;

pub fn Demo() -> impl IntoView {
    let (source, set_source) = signal(0);

watch_throttled(
    move || source.get(),
    move |_, _, _| {
        log!("changed!");
    },
    500.0,
);

   view! { }
}

This really is only shorthand shorthand for watch_with_options(deps, callback, WatchOptions::default().throttle(ms)).

Please note that if the current component is cleaned up before the throttled callback is called, the throttled callback will not be called.

There's also watch_throttled_with_options where you can specify the other watch options (except filter).

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::{watch_throttled_with_options, WatchThrottledOptions};

pub fn Demo() -> impl IntoView {
    let (source, set_source) = signal(0);

watch_throttled_with_options(
    move || source.get(),
    move |_, _, _| {
        log!("changed!");
    },
    500.0,
    WatchThrottledOptions::default().leading(true).trailing(false),
);

   view! { }
}

Recommended Reading

• Debounce vs Throttle: Definitive Visual Guide
• Debouncing and Throttling Explained Through Examples

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server the callback will never be called except if you set immediate to true in which case the callback will be called exactly once.

See also

• leptos::watch
• fn@crate::watch_debounced

Feature

This function is only available if the crate feature watch_throttled is enabled

Types

• struct WatchThrottledOptions

Source

Source • Demo • Docs

watch_with_options

whenever

Shorthand for watching a signal to be true.

Usage

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::whenever;

pub fn Demo() -> impl IntoView {
let (is_ready, set_ready) = signal(false);

whenever(move || is_ready.get(), |v, _, _| log!("{}", v));

    view! { }
}

Callback Function

Same as fn@crate::watch, the callback will be called with callback(input, prev_input, prev_return).

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::whenever;

pub fn Demo() -> impl IntoView {
let (is_ready, set_ready) = signal(false);
whenever(move || is_ready.get(), |value, prev_value, _| {
    log!("before: {prev_value:?}; now: {value}");
});

    view! { }
}

Computed

Same as fn@crate::watch, you can pass a getter function to calculate on each change.

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::whenever;

pub fn Demo() -> impl IntoView {
let (counter, set_counter) = signal(0);
whenever(
    move || counter.get() == 7,
    |_, _, _| log!("counter is 7 now!"),
);

    view! { }
}

Options

Options and defaults are same as fn@watch_with_options.

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::{WatchOptions, whenever_with_options};

pub fn Demo() -> impl IntoView {
let (counter, set_counter) = signal(0);
whenever_with_options(
    move || counter.get() == 7,
    |_, _, _| log!("counter is 7 now!"),
    WatchOptions::default().immediate(true),
);

    view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this works just fine except if you throttle or debounce in which case the callback will never be called except if you set immediate to true in which case the callback will be called exactly once.

Feature

This function is only available if the crate feature whenever is enabled

Source

Source • Docs

signal_debounced

Debounce changing of a Signal value.

Use *_local variants for values that are not Send + Sync.

Demo

Usage

use leptos::prelude::*;
use leptos_use::{signal_debounced, signal_debounced_local};
use std::cell::RefCell;

#[component]
fn Demo() -> impl IntoView {
let (input, set_input) = signal("");
let debounced: Signal<&'static str> = signal_debounced(input, 1000.0);

let (input_local, set_input_local) = signal_local(RefCell::new(0));
let debounced_local: Signal<RefCell<i32>, _> = signal_debounced_local(input_local, 1000.0);

view! { }
}

Options

The usual debounce option max_wait is available.

use leptos::prelude::*;
use leptos_use::{signal_debounced_with_options, signal_debounced_local_with_options, DebounceOptions};
use std::cell::RefCell;

#[component]
fn Demo() -> impl IntoView {
let (input, set_input) = signal("");
let debounced: Signal<&'static str> = signal_debounced_with_options(
    input,
    1000.0,
    DebounceOptions::default().max_wait(Some(500.0))
);

let (input_local, set_input_local) = signal_local(RefCell::new(0));
let debounced_local: Signal<RefCell<i32>, _> = signal_debounced_local_with_options(
    input_local,
    1000.0,
    DebounceOptions::default().max_wait(Some(500.0))
);

view! { }
}

Recommended Reading

• Debounce vs Throttle: Definitive Visual Guide
• Debouncing and Throttling Explained Through Examples

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

Internally this uses setTimeout which is not supported on the server. So usually a throttled signal on the server will simply be ignored.

Feature

This function is only available if the crate feature signal_debounced is enabled

Source

Source • Demo • Docs

signal_throttled

Throttle changing of a Signal value.

Use *_local variants for values that are not Send + Sync.

Demo

Usage

use leptos::prelude::*;
use leptos_use::{signal_throttled, signal_throttled_local};
use std::cell::RefCell;

#[component]
fn Demo() -> impl IntoView {
let (input, set_input) = signal("");
let throttled: Signal<&'static str> = signal_throttled(input, 1000.0);

let (input_local, set_input_local) = signal_local(RefCell::new(0));
let throttled_local: Signal<RefCell<i32>, _> = signal_throttled_local(input_local, 1000.0);

view! { }
}

Options

The usual throttle options leading and trailing are available.

use leptos::prelude::*;
use leptos_use::{signal_throttled_with_options, signal_throttled_local_with_options, ThrottleOptions};
use std::cell::RefCell;

#[component]
fn Demo() -> impl IntoView {
let (input, set_input) = signal("");
let throttled: Signal<&'static str> = signal_throttled_with_options(
    input,
    1000.0,
    ThrottleOptions::default().leading(false).trailing(true)
);

let (input_local, set_input_local) = signal_local(RefCell::new(0));
let throttled_local: Signal<RefCell<i32>, _> = signal_throttled_local_with_options(
    input_local,
    1000.0,
    ThrottleOptions::default().leading(false).trailing(true)
);

view! { }
}

Recommended Reading

• Debounce vs Throttle: Definitive Visual Guide
• Debouncing and Throttling Explained Through Examples

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

Internally this uses setTimeout which is not supported on the server. So usually a throttled signal on the server will simply be ignored.

Feature

This function is only available if the crate feature signal_throttled is enabled

Source

Source • Demo • Docs

sync_signal

Two-way Signals synchronization.

Note: Please consider first if you can achieve your goals with the "Good Options" described in the Leptos book Only if you really have to, use this function. This is, in effect, the "If you really must..." option.

Demo

Usage

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::sync_signal;

#[component]
fn Demo() -> impl IntoView {
let (a, set_a) = signal(1);
let (b, set_b) = signal(2);

let stop = sync_signal((a, set_a), (b, set_b));

log!("a: {}, b: {}", a.get(), b.get()); // a: 1, b: 1

set_b.set(3);

log!("a: {}, b: {}", a.get(), b.get()); // a: 3, b: 3

set_a.set(4);

log!("a: {}, b: {}", a.get(), b.get()); // a: 4, b: 4

view! { }
}

RwSignal

You can mix and match RwSignals and Signal-WriteSignal pairs.

use leptos::prelude::*;
use leptos_use::sync_signal;

#[component]
fn Demo() -> impl IntoView {
let (a, set_a) = signal(1);
let (b, set_b) = signal(2);
let c_rw = RwSignal::new(3);
let d_rw = RwSignal::new(4);

sync_signal((a, set_a), c_rw);
sync_signal(d_rw, (b, set_b));
sync_signal(c_rw, d_rw);


view! { }
}

One directional

You can synchronize a signal only from left to right or right to left.

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::{sync_signal_with_options, SyncSignalOptions, SyncDirection};

#[component]
fn Demo() -> impl IntoView {
let (a, set_a) = signal(1);
let (b, set_b) = signal(2);

let stop = sync_signal_with_options(
    (a, set_a),
    (b, set_b),
    SyncSignalOptions::default().direction(SyncDirection::LeftToRight)
);

set_b.set(3); // doesn't sync

log!("a: {}, b: {}", a.get(), b.get()); // a: 1, b: 3

set_a.set(4);

log!("a: {}, b: {}", a.get(), b.get()); // a: 4, b: 4

view! { }
}

Custom Transform

You can optionally provide custom transforms between the two signals.

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::{sync_signal_with_options, SyncSignalOptions};

#[component]
fn Demo() -> impl IntoView {
let (a, set_a) = signal(10);
let (b, set_b) = signal(2);

let stop = sync_signal_with_options(
    (a, set_a),
    (b, set_b),
    SyncSignalOptions::with_transforms(
        |left| *left * 2,
        |right| *right / 2,
    ),
);

log!("a: {}, b: {}", a.get(), b.get()); // a: 10, b: 20

set_b.set(30);

log!("a: {}, b: {}", a.get(), b.get()); // a: 15, b: 30

view! { }
}

Different Types

SyncSignalOptions::default() is only defined if the two signal types are identical. Otherwise, you have to initialize the options with with_transforms or with_assigns instead of default.

use leptos::prelude::*;
use leptos_use::{sync_signal_with_options, SyncSignalOptions};
use std::str::FromStr;

#[component]
fn Demo() -> impl IntoView {
let (a, set_a) = signal("10".to_string());
let (b, set_b) = signal(2);

let stop = sync_signal_with_options(
    (a, set_a),
    (b, set_b),
    SyncSignalOptions::with_transforms(
        |left: &String| i32::from_str(left).unwrap_or_default(),
        |right: &i32| right.to_string(),
    ),
);

view! { }
}

use leptos::prelude::*;
use leptos_use::{sync_signal_with_options, SyncSignalOptions};
use std::str::FromStr;

#[derive(Clone)]
pub struct Foo {
    bar: i32,
}

#[component]
fn Demo() -> impl IntoView {
let (a, set_a) = signal(Foo { bar: 10 });
let (b, set_b) = signal(2);

let stop = sync_signal_with_options(
    (a, set_a),
    (b, set_b),
    SyncSignalOptions::with_assigns(
        |b: &mut i32, a: &Foo| *b = a.bar,
        |a: &mut Foo, b: &i32| a.bar = *b,
    ),
);

view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server the signals are not continuously synced. If the option immediate is true, the signals are synced once initially. If the option immediate is false, then this function does nothing.

Feature

This function is only available if the crate feature sync_signal is enabled

Types

• enum SyncDirection
• enum SyncTransforms
• struct SyncSignalOptions

Source

Source • Demo • Docs

use_sorted

Reactive sort of iterable

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_sorted;

#[component]
fn Demo() -> impl IntoView {
let source = vec![10, 3, 5, 7, 2, 1, 8, 6, 9, 4];
let sorted: Signal<Vec<i32>> = use_sorted(source); // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

view! { }
}

You can also sort by key or with a compare function.

use leptos::prelude::*;
use leptos_use::{use_sorted_by, use_sorted_by_key};

#[derive(Clone, PartialEq)]
pub struct Person {
    pub name: String,
    pub age: u16,
}

#[component]
fn Demo() -> impl IntoView {
let source = vec![
    Person {
        name: "John".to_string(),
        age: 40,
    },
    Person {
        name: "Jane".to_string(),
        age: 20,
    },
    Person {
        name: "Joe".to_string(),
        age: 30,
    },
    Person {
        name: "Jenny".to_string(),
        age: 22,
    },
];

// sort by key
let sorted: Signal<Vec<Person>> = use_sorted_by_key(
    source.clone(),
    |person: &Person| person.age,
);

// sort with compare function
let sorted: Signal<Vec<Person>> = use_sorted_by(
    source,
    |p1: &Person, p2: &Person| p1.age.cmp(&p2.age),
);

view! { }
}

Please note that these two ways of sorting are equivalent.

Feature

This function is only available if the crate feature use_sorted is enabled

Source

Source • Demo • Docs

header

Get the value of the header with the given name.

This function is only meant to be used on the server. So it is only defined when the feature "ssr" is enabled together with one of the features "axum" or "actix".

Example

use leptos_use::utils::header;

let content_len = header(http::header::CONTENT_LENGTH);

Feature

This function is only available if the crate feature utils/header is enabled

Source

Source • Docs

is_err

Reactive Result::is_err().

Usage

use leptos::prelude::*;
use leptos_use::is_err;

#[component]
fn Demo() -> impl IntoView {
let (example, set_example) = signal(
    if js_sys::Math::random() < 0.5 { Ok("Example") } else { Err(()) }
);

let is_error = is_err(example);

view! { }
}

Feature

This function is only available if the crate feature is_err is enabled

Source

Source • Docs

is_none

Reactive Option::is_none().

Usage

use leptos::prelude::*;
use leptos_use::is_none;

#[component]
fn Demo() -> impl IntoView {
let (example, set_example) = signal(
    if js_sys::Math::random() < 0.5 { Some("Example") } else { None }
);

let is_empty = is_none::<_, &str>(example);

view! { }
}

Feature

This function is only available if the crate feature is_none is enabled

Source

Source • Docs

is_ok

Reactive Result::is_ok().

Usage

use leptos::prelude::*;
use leptos_use::is_ok;

#[component]
fn Demo() -> impl IntoView {
let (example, set_example) = signal(
    if js_sys::Math::random() < 0.5 { Ok("Example") } else { Err(()) }
);

let is_ok = is_ok(example);

view! { }
}

Feature

This function is only available if the crate feature is_ok is enabled

Source

Source • Docs

is_some

Reactive Option::is_some().

Usage

use leptos::prelude::*;
use leptos_use::is_some;

#[component]
fn Demo() -> impl IntoView {
let (example, set_example) = signal(
    if js_sys::Math::random() < 0.5 { Some("Example") } else { None }
);

let not_empty = is_some::<_, &str>(example);

view! { }
}

Feature

This function is only available if the crate feature is_some is enabled

Source

Source • Docs

use_cycle_list

Cycle through a list of items.

Demo

Usage

use leptos::prelude::*;
use leptos::logging::log;
use leptos_use::{use_cycle_list, UseCycleListReturn};

#[component]
fn Demo() -> impl IntoView {
let UseCycleListReturn { state, next, prev, .. } = use_cycle_list(
    vec!["Dog", "Cat", "Lizard", "Shark", "Whale", "Dolphin", "Octopus", "Seal"]
);

log!("{}", state.get()); // "Dog"

prev();

log!("{}", state.get()); // "Seal"

view! { }
}

Feature

This function is only available if the crate feature use_cycle_list is enabled

Types

• struct UseCycleListOptions
• struct UseCycleListReturn

Source

Source • Demo • Docs

use_debounce_fn

Debounce execution of a function.

Debounce is an overloaded waiter: If you keep asking him your requests will be ignored until you stop and give him some time to think about your latest inquiry.

Demo

Usage

use leptos::prelude::*;
use leptos::ev::resize;
use leptos_use::use_debounce_fn;

#[component]
fn Demo() -> impl IntoView {
let mut debounced_fn = use_debounce_fn(
    || {
        // do something
    },
    1000.0,
);

window_event_listener(resize, move |_| { debounced_fn(); });
   view! { }
}

Please note that if the current component is cleaned up before the throttled callback is called, the throttled callback will not be called.

You can also pass options to use_debounce_fn_with_options with a maximum wait time, similar to lodash debounce.

use leptos::prelude::*;
use leptos::ev::resize;
use leptos_use::use_debounce_fn_with_options;
use leptos_use::utils::DebounceOptions;

#[component]
fn Demo() -> impl IntoView {
let mut debounced_fn = use_debounce_fn_with_options(
    || {
        // do something
    },
    1000.0,
    DebounceOptions::default()
        .max_wait(Some(5000.0)),
);

window_event_listener(resize, move |_| { debounced_fn(); });
   view! { }
}

Currently there is no way to use a function with a return value. Please open an issue if you need this.

If you want to throttle a function that takes an argument there are also the versions use_debounce_fn_with_arg and use_debounce_fn_with_arg_and_options.

SendWrapped Return

The returned closure is a sendwrapped function. It can only be called from the same thread that called use_debounce_....

Recommended Reading

• Debounce vs Throttle: Definitive Visual Guide
• Debouncing and Throttling Explained Through Examples

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

Internally this uses setTimeout which is not supported on the server. So usually calling a debounced function on the server will simply be ignored.

Feature

This function is only available if the crate feature use_debounce_fn is enabled

Source

Source • Demo • Docs

use_derive_signal!

Macro to easily create helper functions that derive a signal using a piece of code.

See is_ok or use_to_string as examples.

use_supported

SSR compatibe is_supported

Usage

use leptos::prelude::*;
use leptos_use::{use_supported, js};
use wasm_bindgen::JsValue;

pub fn Demo() -> impl IntoView {
let is_supported = use_supported(
    || js!("getBattery" in &window().navigator())
);

if is_supported.get() {
    // do something
}
   view! { }
}

Feature

This function is only available if the crate feature use_supported is enabled

Source

Source • Docs

use_throttle_fn

Throttle execution of a function. Especially useful for rate limiting execution of handlers on events like resize and scroll.

Throttle is a spring that throws balls: After a ball flies out it needs some time to shrink back, so it cannot throw any more balls until it's ready.

Demo

Usage

use leptos::prelude::*;
use leptos_use::use_throttle_fn;

#[component]
fn Demo() -> impl IntoView {
let mut throttled_fn = use_throttle_fn(
    || {
        // do something, it will be called at most 1 time per second
    },
    1000.0,
);
view! {
    <button on:click=move |_| { throttled_fn(); }>
        "Smash me!"
    </button>
}
}

Please note that if the current component is cleaned up before the throttled callback is called, the throttled callback will not be called.

You can provide options when you use use_throttle_fn_with_options.

use leptos::prelude::*;
use leptos_use::{ThrottleOptions, use_throttle_fn_with_options};
#[component]
fn Demo() -> impl IntoView {
let throttled_fn = use_throttle_fn_with_options(
    || {
        // do something, it will be called at most 1 time per second
    },
    1000.0,
    ThrottleOptions::default()
        .leading(true)
        .trailing(true),
);
   view! { }
}

If you want to throttle a function that takes an argument there are also the versions use_throttle_fn_with_arg and use_throttle_fn_with_arg_and_options.

SendWrapped Return

The returned closure is a sendwrapped function. It can only be called from the same thread that called use_throttle_....

Recommended Reading

• Debounce vs Throttle: Definitive Visual Guide
• Debouncing and Throttling Explained Through Examples

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

Internally this uses setTimeout which is not supported on the server. So usually calling a throttled function on the server will simply be ignored.

Feature

This function is only available if the crate feature use_throttle_fn is enabled

Source

Source • Demo • Docs

use_to_string

Reactive ToString::to_string().

Usage

use leptos::prelude::*;
use leptos_use::use_to_string;

#[component]
fn Demo() -> impl IntoView {
let (number, set_number) = signal(3.14_f64);
let str = use_to_string::<_, f64>(number);

view! { }
}

Feature

This function is only available if the crate feature use_to_string is enabled

Source

Source • Docs

use_toggle

A boolean switcher with utility functions.

Demo

Usage

use leptos::*;
use leptos_use::{use_toggle, UseToggleReturn};

#[component]
fn Demo() -> impl IntoView {
let UseToggleReturn { toggle, value, set_value } = use_toggle(true);

view! { }
}

See also

• fn@crate::use_cycle_list

Feature

This function is only available if the crate feature use_toggle is enabled

Types

• struct UseToggleReturn

Source

Source • Demo • Docs

use_intl_number_format

Reactive Intl.NumberFormat.

Demo

Usage

In basic use without specifying a locale, a formatted string in the default locale and with default options is returned.

use leptos::prelude::*;
use leptos_use::{use_intl_number_format, UseIntlNumberFormatOptions};

#[component]
fn Demo() -> impl IntoView {
let (number, set_number) = signal(3500);

let number_format = use_intl_number_format(UseIntlNumberFormatOptions::default());

let formatted = number_format.format::<u16>(number); // "3,500" if in US English locale

view! { }
}

Using locales

This example shows some of the variations in localized number formats. In order to get the format of the language used in the user interface of your application, make sure to specify that language (and possibly some fallback languages) using the locales argument:

use leptos::prelude::*;
use leptos_use::{use_intl_number_format, UseIntlNumberFormatOptions};

#[component]
fn Demo() -> impl IntoView {
let number = 123456.789_f32;

// German uses comma as decimal separator and period for thousands
let number_format = use_intl_number_format(
    UseIntlNumberFormatOptions::default().locale("de-DE"),
);
let formatted = number_format.format::<f32>(number); // 123.456,789

// Arabic in most Arabic speaking countries uses real Arabic digits
let number_format = use_intl_number_format(
    UseIntlNumberFormatOptions::default().locale("ar-EG"),
);
let formatted = number_format.format::<f32>(number); // ١٢٣٤٥٦٫٧٨٩

// India uses thousands/lakh/crore separators
let number_format = use_intl_number_format(
    UseIntlNumberFormatOptions::default().locale("en-IN"),
);
let formatted = number_format.format::<f32>(number); // 1,23,456.789

// the nu extension key requests a numbering system, e.g. Chinese decimal
let number_format = use_intl_number_format(
    UseIntlNumberFormatOptions::default().locale("zh-Hans-CN-u-nu-hanidec"),
);
let formatted = number_format.format::<f32>(number); // 一二三,四五六.七八九

// when requesting a language that may not be supported, such as
// Balinese, include a fallback language, in this case Indonesian
let number_format = use_intl_number_format(
    UseIntlNumberFormatOptions::default().locales(vec!["ban".to_string(), "id".to_string()]),
);
let formatted = number_format.format::<f32>(number); // 123.456,789


view! { }
}

Using options

The results can be customized in multiple ways.

use leptos::prelude::*;
use leptos_use::{NumberStyle, UnitDisplay, use_intl_number_format, UseIntlNumberFormatOptions};

#[component]
fn Demo() -> impl IntoView {
let number = 123456.789_f64;

// request a currency format
let number_format = use_intl_number_format(
    UseIntlNumberFormatOptions::default()
        .locale("de-DE")
        .style(NumberStyle::Currency)
        .currency("EUR"),
);
let formatted = number_format.format::<f64>(number); // 123.456,79 €

// the Japanese yen doesn't use a minor unit
let number_format = use_intl_number_format(
    UseIntlNumberFormatOptions::default()
        .locale("ja-JP")
        .style(NumberStyle::Currency)
        .currency("JPY"),
);
let formatted = number_format.format::<f64>(number); // ￥123,457

// limit to three significant digits
let number_format = use_intl_number_format(
    UseIntlNumberFormatOptions::default()
        .locale("en-IN")
        .maximum_significant_digits(3),
);
let formatted = number_format.format::<f64>(number); // 1,23,000

// Formatting with units
let number_format = use_intl_number_format(
    UseIntlNumberFormatOptions::default()
        .locale("pt-PT")
        .style(NumberStyle::Unit)
        .unit("kilometer-per-hour"),
);
let formatted = number_format.format::<i32>(50); // 50 km/h

let number_format = use_intl_number_format(
    UseIntlNumberFormatOptions::default()
        .locale("en-GB")
        .style(NumberStyle::Unit)
        .unit("liter")
        .unit_display(UnitDisplay::Long),
);
let formatted = number_format.format::<i32>(16); // 16 litres

view! { }
}

For an exhaustive list of options see UseIntlNumberFormatOptions.

Formatting ranges

Apart from the format method, the format_range method can be used to format a range of numbers. Please see UseIntlNumberFormatReturn::format_range for details.

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

Since Intl.NumberFormat is a JavaScript API it is not available on the server. That's why it falls back to a simple call to format!() on the server.

Feature

This function is only available if the crate feature use_intl_number_format is enabled

Types

• enum CompactDisplay
• enum CurrencyDisplay
• enum CurrencySign
• enum LocaleMatcher
• enum Notation
• enum SignDisplay
• enum NumberStyle
• enum UnitDisplay
• enum NumberGrouping
• enum RoundingMode
• enum RoundingPriority
• enum TrailingZeroDisplay
• struct UseIntlNumberFormatOptions

Source

Source • Demo • Docs

use_locale

Reactive locale matching.

Returns the first matching locale given by fn@crate::use_locales that is also found in the supported list. In case there is no match, then the first locale in supported will be returned.

If supported is empty, this function will panic!

Matching is done by using the fn@unic_langid::LanguageIdentifier::matches method.

Demo

Usage

use leptos::*;
use leptos_use::use_locale;
use unic_langid::langid_slice;

#[component]
fn Demo() -> impl IntoView {
let locale = use_locale(langid_slice!["en", "de", "fr"]);

view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

See fn@crate::use_locales

Feature

This function is only available if the crate feature use_locale is enabled

Source

Source • Demo • Docs

use_locales

Reactive locales.

If called on the client-side this function returns the value of navigator.languages and listens for changes to that property.

See "Server-Side Rendering" below.

Demo

Usage

use leptos::*;
use leptos_use::use_locales;

#[component]
fn Demo() -> impl IntoView {
let locales = use_locales();

view! { }
}

Server-Side Rendering

Make sure you follow the instructions in Server-Side Rendering.

On the server this returns the parsed value of the accept-language header.

If you're using axum you have to enable the "axum" feature in your Cargo.toml. In case it's actix-web enable the feature "actix".

Bring your own header

In case you're neither using Axum nor Actix or the default implementation is not to your liking, you can provide your own way of reading the language header value using the option crate::UseLocalesOptions::ssr_lang_header_getter.

Feature

This function is only available if the crate feature use_locales is enabled

Types

• struct UseLocalesOptions

Source

Source • Demo • Docs

use_abs

Reactive abs().

Demo

Usage

use leptos::prelude::*;
use leptos_use::math::use_abs;

#[component]
fn Demo() -> impl IntoView {
let (value, set_value) = signal(-32.25);
let result: Signal<f64> = use_abs(value); // 32.25

assert_eq!(result.get(), 32.25);
view! { }
}

Feature

This function is only available if the crate feature math is enabled

Source

Source • Demo • Docs

use_and

Reactive AND condition.

Demo

Usage

use leptos::prelude::*;
use leptos_use::math::use_and;

#[component]
fn Demo() -> impl IntoView {
let (a, set_a) = signal(true);
let (b, set_b) = signal(false);

let a_and_b = use_and(a, b);

view! { }
}

Feature

This function is only available if the crate feature math is enabled

Source

Source • Demo • Docs

use_ceil

Reactive ceil().

Demo

Usage

use leptos::prelude::*;
use leptos_use::math::use_ceil;

#[component]
fn Demo() -> impl IntoView {
let (value, set_value) = signal(44.15);
let result: Signal<f64> = use_ceil(value); // 45

assert_eq!(result.get(), 45.0);
view! { }
}

Feature

This function is only available if the crate feature math is enabled

Source

Source • Demo • Docs

use_floor

Reactive floor().

Demo

Usage

use leptos::prelude::*;
use leptos_use::math::use_floor;

#[component]
fn Demo() -> impl IntoView {
let (value, set_value) = signal(45.95);
let result: Signal<f64> = use_floor(value); // 45

assert_eq!(result.get(), 45.0);
view! { }
}

Feature

This function is only available if the crate feature math is enabled

Source

Source • Demo • Docs

use_max

Reactive max().

Works with any container that implements IntoIterator (Vec, HashSet, ...) with any elements that implement PartialOrd and Clone (floats, ints, strings, ...).

If the container is empty or only contains non comparable values like NaN, it returns None. Otherwise it returns the Some(<largest value>) in the container.

Usage

use leptos::prelude::*;
use leptos_use::math::use_max;

#[component]
fn Demo() -> impl IntoView {
let (values, set_values) = signal(vec![1.0, 2.0, 3.0, f32::NAN, 4.0, 5.0]);
let result = use_max::<Vec<f32>, _, _>(values); // Some(5.0)

assert_eq!(result.get(), Some(5.0));
view! { }
}

Feature

This function is only available if the crate feature math is enabled

Source

Source • Docs

use_min

Reactive min().

Works with any container that implements IntoIterator (Vec, HashSet, ...) with any elements that implement PartialOrd and Clone (floats, ints, strings, ...).

If the container is empty or only contains non comparable values like NaN, it returns None. Otherwise it returns the Some(<smallest value>) in the container.

Usage

use leptos::prelude::*;
use leptos_use::math::use_min;

#[component]
fn Demo() -> impl IntoView {
let (values, set_values) = signal(vec![1.0, 2.0, 3.0, f32::NAN, 4.0, 5.0]);
let result = use_min::<Vec<f32>, _, _>(values); // Some(1.0)

assert_eq!(result.get(), Some(1.0));
view! { }
}

Feature

This function is only available if the crate feature math is enabled

Source

Source • Docs

use_not

Reactive NOT condition.

Demo

Usage

use leptos::prelude::*;
use leptos_use::math::use_not;

#[component]
fn Demo() -> impl IntoView {
let (a, set_a) = signal(true);

let not_a = use_not(a);

view! { }
}

See also

• use_and
• use_or

Feature

This function is only available if the crate feature math is enabled

Source

Source • Demo • Docs

use_or

Reactive OR condition.

Demo

Usage

use leptos::prelude::*;
use leptos_use::math::use_or;

#[component]
fn Demo() -> impl IntoView {
let (a, set_a) = signal(true);
let (b, set_b) = signal(false);

let a_or_b = use_or(a, b);

view! { }
}

Feature

This function is only available if the crate feature math is enabled

Source

Source • Demo • Docs

use_round

Reactive round().

Demo

Usage

use leptos::prelude::*;
use leptos_use::math::use_round;

#[component]
fn Demo() -> impl IntoView {
let (value, set_value) = signal(45.95);
let result: Signal<f64> = use_round(value); // 46

assert_eq!(result.get(), 46.0);
view! { }
}

Feature

This function is only available if the crate feature math is enabled

Source

Source • Demo • Docs