Boxed Number Slices: `Box<[u8]>`, `Box<[i8]>`, `Box<[u16]>`, `Box<[i16]>`, `Box<[u32]>`, `Box<[i32]>`, `Box<[u64]>`, `Box<[i64]>`, `Box<[f32]>`, and `Box<[f64]>`

`T` parameter	`&T` parameter	`&mut T` parameter	`T` return value	`Option<T>` parameter	`Option<T>` return value	JavaScript representation
Yes	No	No	Yes	Yes	Yes	A JavaScript `TypedArray` of the appropriate type (`Int32Array`, `Uint8Array`, etc...)

Note that the contents of the slice are copied into the JavaScript TypedArray from the Wasm linear memory when returning a boxed slice to JavaScript, and vice versa when receiving a JavaScript TypedArray as a boxed slice in Rust.

Example Rust Usage

#![allow(unused)]
fn main() {
use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub fn take_boxed_number_slice_by_value(x: Box<[f64]>) {}

#[wasm_bindgen]
pub fn return_boxed_number_slice() -> Box<[u32]> {
    (0..42).collect::<Vec<u32>>().into_boxed_slice()
}

#[wasm_bindgen]
pub fn take_option_boxed_number_slice(x: Option<Box<[u8]>>) {}

#[wasm_bindgen]
pub fn return_option_boxed_number_slice() -> Option<Box<[i32]>> {
    None
}
}

Example JavaScript Usage

import {
  take_boxed_number_slice_by_value,
  return_boxed_number_slice,
  take_option_boxed_number_slice,
  return_option_boxed_number_slice,
} from './guide_supported_types_examples';

take_boxed_number_slice_by_value(new Uint8Array(100));

let x = return_boxed_number_slice();
console.log(x instanceof Uint32Array); // true

take_option_boxed_number_slice(null);
take_option_boxed_number_slice(undefined);
take_option_boxed_number_slice(new Int16Array(256));

let y = return_option_boxed_number_slice();
if (y == null) {
  // ...
} else {
  console.log(x instanceof Int32Array); // true
}