<meta charset="utf-8"/>
# `wasm-bindgen`
**Facilitating high-level interactions between wasm modules and JavaScript.**
[](https://travis-ci.org/rustwasm/wasm-bindgen)
[](https://ci.appveyor.com/project/alexcrichton/wasm-bindgen)
[](https://crates.io/crates/wasm-bindgen)
[](https://crates.io/crates/wasm-bindgen)
[](https://docs.rs/wasm-bindgen)
Import JavaScript things into Rust and export Rust things to JavaScript.
```rust
extern crate wasm_bindgen;
use wasm_bindgen::prelude::*;
// Import the `window.alert` function from the Web.
#[wasm_bindgen]
extern "C" {
fn alert(s: &str);
}
// Export a `greet` function from Rust to JavaScript, that alerts a
// hello message.
#[wasm_bindgen]
pub fn greet(name: &str) {
alert(&format!("Hello, {}!", name));
}
```
Use exported Rust things from JavaScript with ECMAScript modules!
```js
import { greet } from "./hello_world";
greet("World!");
```
## Features
* **Lightweight.** Only pay for what you use. `wasm-bindgen` only generates
bindings and glue for the JavaScript imports you actually use and Rust
functionality that you export. For example, importing and using the
`document.querySelector` method doesn't cause `Node.prototype.appendChild` or
`window.alert` to be included in the bindings as well.
* **ECMAScript modules.** Just import WebAssembly modules the same way you would
import JavaScript modules. Future compatible with [WebAssembly modules and
ECMAScript modules integration][wasm-es-modules].
* **Designed with the ["host bindings" proposal][host-bindings] in mind.**
Eventually, there won't be any JavaScript shims between Rust-generated wasm
functions and native DOM methods. Because the wasm functions are statically
type checked, some of those native methods' dynamic type checks should become
unnecessary, promising to unlock even-faster-than-JavaScript DOM access.
[wasm-es-modules]: https://github.com/WebAssembly/esm-integration
[host-bindings]: https://github.com/WebAssembly/host-bindings/blob/master/proposals/host-bindings/Overview.md
## Guide
[**📚 Read the `wasm-bindgen` guide here! 📚**](https://rustwasm.github.io/wasm-bindgen)
## API Docs
- [wasm-bindgen](https://rustwasm.github.io/wasm-bindgen/api/wasm_bindgen/)
- [js-sys](https://rustwasm.github.io/wasm-bindgen/api/js_sys/)
- [web-sys](https://rustwasm.github.io/wasm-bindgen/api/web_sys/)
## License
This project is licensed under either of
* Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
http://www.apache.org/licenses/LICENSE-2.0)
* MIT license ([LICENSE-MIT](LICENSE-MIT) or
http://opensource.org/licenses/MIT)
at your option.
## Contribution
**[See the "Contributing" section of the guide for information on
hacking on `wasm-bindgen`!][contributing]**
Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in this project by you, as defined in the Apache-2.0 license,
shall be dual licensed as above, without any additional terms or conditions.
[contributing]: https://rustwasm.github.io/wasm-bindgen/contributing/index.html