Struct Js 

pub struct Js;

Available on crate feature js only.

⬡ 🛠️ Javascript-related operations.

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^{📍 lang/prog/ffi/js}

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See also: Web.

Implementations

impl Js

pub fn console() -> JsConsole

Returns the JsConsole namespace struct.

impl Js

Strings

pub fn read_str( buffer: &mut [u8], write_fn: impl FnMut(*mut u8, js_uint32) -> js_int32, ) -> &str

Reads a JS string into a Rust &str backed by the given buffer, truncating if the buffer is too small.

Panic

Panics if the result is not valid UTF-8.

pub fn read_string( write_fn: impl FnMut(*mut u8, js_uint32) -> js_int32, ) -> String

Available on unsafe·· and crate feature alloc only.

Allocates a String by calling a JS-backed FFI fn that writes a UTF-8 string into WASM memory. Allocates a new String from JS (auto-sizing).

• Uses a dynamic buffer, starting with 128 bytes of capacity.
• Retries with exact required capacity if truncation is detected.

pub fn read_string_capped( cap: js_uint32, truncate: bool, write_fn: impl FnMut(*mut u8, js_uint32) -> js_int32, ) -> String

Available on unsafe·· and crate feature alloc only.

Allocates a String by calling a JS-backed FFI fn that writes a UTF-8 string into WASM memory.

• Uses a dynamic buffer, starting with the given capacity.
• Retries with exact required capacity if truncation is detected (unless truncate = true).
• Assumes the FFI fn returns js_int32: positive = bytes written, negative = required size.

Trait Implementations

impl Debug for Js

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.