Struct Js

pub struct Js;

Available on crate feature js only.

A Javascript namespace.

Methods

• core APis
  • console
  • events
  • history
  • permissions
• extended APis
  • media & graphics
    • canvas
  • performance & optimization

Implementations

impl Js

Web API console

• https://developer.mozilla.org/en-US/docs/Web/API/console

pub fn console_debug(text: &str)

Available on crate feature unsafe_ffi and WebAssembly only.

(debug) Outputs a message to the console with the debug log level.

pub fn console_error(text: &str)

Available on crate feature unsafe_ffi and WebAssembly only.

(error) Outputs a message to the console with the error log level.

pub fn console_info(text: &str)

Available on crate feature unsafe_ffi and WebAssembly only.

(info) Outputs a message to the console with the info log level.

pub fn console_log(text: &str)

Available on crate feature unsafe_ffi and WebAssembly only.

(log) Outputs a message to the console.

pub fn console_trace()

Available on crate feature unsafe_ffi and WebAssembly only.

(trace) Outputs a stack trace.

pub fn console_warn(text: &str)

Available on crate feature unsafe_ffi and WebAssembly only.

(warn) Outputs a message to the console with the warning log level.

pub fn console_group(text: &str)

Available on crate feature unsafe_ffi and WebAssembly only.

(group) Creates a new inline group, indenting all following output by another level.

pub fn console_group_end()

Available on crate feature unsafe_ffi and WebAssembly only.

(groupEnd) Exits the current inline group.

impl Js

Web API Events

Provides event handling for interactivity. Uses Rust function pointers to manage callbacks.

• https://developer.mozilla.org/en-US/docs/Web/API/Event
• https://developer.mozilla.org/en-US/docs/Web/API/EventTarget
• https://developer.mozilla.org/en-US/docs/Web/API/EventListener

pub fn event_add_listener( element: &str, event: JsEvent, rust_fn: extern "C" fn(), )

Available on crate feature unsafe_ffi and WebAssembly only.

(addEventListener) Attaches a Rust function event listener from an element.

pub fn event_remove_listener( element: &str, event: JsEvent, rust_fn: extern "C" fn(), )

Available on crate feature unsafe_ffi and WebAssembly only.

(removeEventListener) Removes a a Rust function event listener from an element.

pub fn event_add_listener_js(element: &str, event: JsEvent, js_fn_name: &str)

Available on crate feature unsafe_ffi and WebAssembly only.

(addEventListenerJs) Attaches a JavaScript function event linstener to an element.

pub fn event_remove_listener_js(element: &str, event: JsEvent, js_fn_name: &str)

Available on crate feature unsafe_ffi and WebAssembly only.

(removeEventListenerJs) Removes a JavaScript function event listener from an element.

#[no_mangle]

pub unsafe extern "C" fn wasm_callback(callback_ptr: usize)

Available on crate feature unsafe_ffi and WebAssembly only.

Callback dispatcher for WebAssembly events.

• This function is used by JavaScript to invoke a Rust function pointer.
• It allows Rust event listeners to execute when triggered by JS.
• The callback_ptr is a function pointer cast from JS, which is then transmuted into a callable Rust function.

Safety

callback_ptr must be a valid function pointer.

Example

#[unsafe(no_mangle)]
pub extern "C" fn my_callback() {
    Js::console_log("Button clicked!");
}
Js::event_add_listener("#my_button", JsEvent::Click, my_callback);

impl Js

Web API history & navigation

• https://developer.mozilla.org/en-US/docs/Web/API/History
• https://developer.mozilla.org/en-US/docs/Web/API/Location

pub fn history_back()

Available on crate feature unsafe_ffi and WebAssembly only.

(back) Moves the browser back one step in the session history.

pub fn history_forward()

Available on crate feature unsafe_ffi and WebAssembly only.

(forward) Moves the browser forward one step in the session history.

pub fn history_go(delta: i32)

Available on crate feature unsafe_ffi and WebAssembly only.

(go) Moves the browser to a specific point in the session history. Use negative values to go back, positive to go forward.

pub fn history_push_state(state: &str, title: &str, url: &str)

Available on crate feature unsafe_ffi and WebAssembly only.

(pushState) Adds an entry to the session history stack.

pub fn history_replace_state(state: &str, title: &str, url: &str)

Available on crate feature unsafe_ffi and WebAssembly only.

(replaceState) Modifies the current history entry without creating a new one.

pub fn location_reload()

Available on crate feature unsafe_ffi and WebAssembly only.

(reload) Reloads the current document.

pub fn location_assign(url: &str)

Available on crate feature unsafe_ffi and WebAssembly only.

(assign) Loads the specified URL.

pub fn location_replace(url: &str)

Available on crate feature unsafe_ffi and WebAssembly only.

(replace) Replaces the current document with the specified URL without creating a new entry in the history.

impl Js

Web API permissions

• https://developer.mozilla.org/en-US/docs/Web/API/Permissions_API

pub fn permissions_query(permission: JsPermission) -> JsPermissionState

Available on crate feature unsafe_ffi and WebAssembly only.

(query) Queries the status of a given permission.

Returns Granted, Denied, Prompt, or Unknown if unsupported.

impl Js

Web API canvas

• https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D
• https://html.spec.whatwg.org/multipage/canvas.html

pub fn set_canvas(id: &str)

Available on crate feature unsafe_ffi and WebAssembly only.

Sets the active canvas by ID.

pub fn fill_style(r: u8, g: u8, b: u8)

Available on crate feature unsafe_ffi and WebAssembly only.

(fillStyle) Sets the color or style for filling shapes.

pub fn stroke_style(r: u8, g: u8, b: u8)

Available on crate feature unsafe_ffi and WebAssembly only.

(strokeStyle) Sets the color or style for lines.

pub fn fill_rect(x: f64, y: f64, w: f64, h: f64)

Available on crate feature unsafe_ffi and WebAssembly only.

(fillRect) Draws a filled rectangle.

pub fn draw_line(x1: f64, y1: f64, x2: f64, y2: f64)

Available on crate feature unsafe_ffi and WebAssembly only.

pub fn draw_circle(x: f64, y: f64, radius: f64)

Available on crate feature unsafe_ffi and WebAssembly only.

pub fn fill_text(text: &str, x: f64, y: f64)

Available on crate feature unsafe_ffi and WebAssembly only.

(fillText) Draws a filled text string at the specified coordinates

impl Js

Web API time

pub fn get_time() -> f64

Available on crate feature unsafe_ffi and WebAssembly only.