diff --git a/src/js.rs b/src/js.rs index fde3402f7..c803cd35c 100644 --- a/src/js.rs +++ b/src/js.rs @@ -112,6 +112,13 @@ extern { extern { pub type Array; + /// The length property of an object which is an instance of type Array sets or returns the number of elements in that array. + /// The value is an unsigned, 32-bit integer that is always numerically greater than the highest index in the array. + /// + /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/length + #[wasm_bindgen(method, getter, structural)] + pub fn length(this: &Array) -> u32; + /// The indexOf() method returns the first index at which a given element can be found in the array, or -1 if it is not present. /// /// http://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/indexOf diff --git a/tests/all/js_globals/Array.rs b/tests/all/js_globals/Array.rs index ae6f893eb..4f62a6d16 100644 --- a/tests/all/js_globals/Array.rs +++ b/tests/all/js_globals/Array.rs @@ -422,3 +422,37 @@ fn includes() { "#) .test() } + + +#[test] +fn length() { + project() + .file("src/lib.rs", r#" + #![feature(proc_macro, wasm_custom_section)] + + extern crate wasm_bindgen; + use wasm_bindgen::prelude::*; + use wasm_bindgen::js; + + #[wasm_bindgen] + pub fn array_length(this: &js::Array) -> u32 { + this.length() + } + + "#) + .file("test.ts", r#" + import * as assert from "assert"; + import * as wasm from "./out"; + + export function test() { + let characters = [8, 5, 4, 3, 1, 2] + let charactersLength = wasm.array_length(characters); + assert.equal(charactersLength, 6); + + var empty : number[] = []; + let emptyLength = wasm.array_length(empty); + assert.equal(emptyLength, 0); + } + "#) + .test() +}