| # `js-sys` |
| |
| The [`js-sys` crate][js-sys] provides raw bindings to all the global APIs |
| guaranteed to exist in every JavaScript environment by the ECMAScript standard, |
| and its source lives at [`wasm-bindgen/crates/js-sys`][src]. With the `js-sys` |
| crate, we can work with `Object`s, `Array`s, `Function`s, `Map`s, `Set`s, |
| etc... without writing the `#[wasm_bindgen]` imports by hand. |
| |
| Documentation for the published version of this crate is available on |
| [docs.rs][docsrs] but you can also check out the [master branch |
| documentation][masterdoc] for the crate. |
| |
| [docsrs]: https://docs.rs/js-sys |
| [masterdoc]: https://rustwasm.github.io/wasm-bindgen/api/js_sys/ |
| [src]: https://github.com/rustwasm/wasm-bindgen/tree/master/crates/js-sys |
| |
| For example, we can invoke JavaScript [`Function`][mdn-function] callbacks and |
| time how long they take to execute with [`Date.now()`][mdn-date-now], and we |
| don't need to write any JS imports ourselves: |
| |
| ```rust |
| use wasm_bindgen::prelude::*; |
| |
| #[wasm_bindgen] |
| pub fn timed(callback: &js_sys::Function) -> f64 { |
| let then = js_sys::Date::now(); |
| callback.apply(JsValue::null(), &js_sys::Array::new()).unwrap(); |
| let now = js_sys::Date::now(); |
| now - then |
| } |
| ``` |
| |
| The `js-sys` crate doesn't contain bindings to any Web APIs like |
| [`document.querySelectorAll`][mdn-qsa]. These will be part of the |
| [`web-sys`][web-sys] crate. |
| |
| [MDN]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects |
| [js-sys]: https://crates.io/crates/js-sys |
| [issue]: https://github.com/rustwasm/wasm-bindgen/issues/275 |
| [mdn-function]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function |
| [mdn-qsa]: https://developer.mozilla.org/en-US/docs/Web/API/Document/querySelectorAll |
| [web-sys]: https://crates.io/crates/web-sys |
| [web-sys-contributing]: https://rustwasm.github.io/wasm-bindgen/web-sys.html |
| [web-sys-issues]: https://github.com/rustwasm/wasm-bindgen/issues?q=is%3Aissue+is%3Aopen+label%3Aweb-sys |
| [mdn-date-now]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/now |
