Hello, World! - The wasm-bindgen Guide (original) (raw)

  1. Introduction
  2. 1. Examples
    1. 1.1. Hello, World!
    2. 1.2. Using console.log
    3. 1.3. Small Wasm files
    4. 1.4. Without a Bundler
    5. 1.5. Synchronous Instantiation
    6. 1.6. Importing functions from JS
    7. 1.7. Working with char
    8. 1.8. js-sys: WebAssembly in WebAssembly
    9. 1.9. web-sys: DOM hello world
    10. 1.10. web-sys: Closures
    11. 1.11. web-sys: performance.now
    12. 1.12. web-sys: using fetch
    13. 1.13. web-sys: Weather report
    14. 1.14. web-sys: canvas hello world
    15. 1.15. web-sys: canvas Julia set
    16. 1.16. web-sys: WebAudio
    17. 1.17. web-sys: WebGL
    18. 1.18. web-sys: WebSockets
    19. 1.19. web-sys: WebRTC DataChannel
    20. 1.20. web-sys: requestAnimationFrame
    21. 1.21. web-sys: A Simple Paint Program
    22. 1.22. web-sys: Wasm in Web Worker
    23. 1.23. Parallel Raytracing
    24. 1.24. Wasm Audio Worklet
    25. 1.25. web-sys: A TODO MVC App
  4. 2. Reference
    1. 2.1. Deployment
    2. 2.2. JS snippets
    3. 2.3. Static JS Objects
    4. 2.4. Passing Rust Closures to JS
    5. 2.5. Receiving JS Closures in Rust
    6. 2.6. Promises and Futures
    7. 2.7. Iterating over JS Values
    8. 2.8. Arbitrary Data with Serde
    9. 2.9. Accessing Properties of Untyped JS Values
    10. 2.10. Working with Duck-Typed Interfaces
    11. 2.11. Command Line Interface
    12. 2.12. Optimizing for Size
    13. 2.13. Supported Rust Targets
    14. 2.14. Supported Browsers
    15. 2.15. Support for Weak References
    16. 2.16. Support for Reference Types
    17. 2.17. Supported Types
      1. 2.17.1. Imported JavaScript Types
      2. 2.17.2. Exported Rust Types
      3. 2.17.3. JsValue
      4. 2.17.4. Box<[T]> and Vec
      5. 2.17.5. *const T and *mut T
      6. 2.17.6. NonNull
      7. 2.17.7. Numbers
      8. 2.17.8. bool
      9. 2.17.9. char
      10. 2.17.10. str
      11. 2.17.11. String
      12. 2.17.12. Number Slices
      13. 2.17.13. Boxed Number Slices
      14. 2.17.14. Result<T, E>
    19. 2.18. #[wasm_bindgen] Attributes
      1. 2.18.1. On JavaScript Imports
        1. 2.18.1.1. catch
          1. 2.18.1.2. constructor
          2. 2.18.1.3. extends
          3. 2.18.1.4. getter and setter
          4. 2.18.1.5. final
          5. 2.18.1.6. indexing_getter, indexing_setter, and indexing_deleter
          6. 2.18.1.7. js_class = "Blah"
          7. 2.18.1.8. js_name
          8. 2.18.1.9. js_namespace
          9. 2.18.1.10. method
          10. 2.18.1.11. module = "blah"
          11. 2.18.1.12. raw_module = "blah"
          12. 2.18.1.13. no_deref
          13. 2.18.1.14. static_method_of = Blah
          14. 2.18.1.15. structural
          15. 2.18.1.16. typescript_type
          16. 2.18.1.17. variadic
          17. 2.18.1.18. vendor_prefix
      3. 2.18.2. On Rust Exports
        1. 2.18.2.1. constructor
          1. 2.18.2.2. js_name = Blah
          2. 2.18.2.3. js_class = Blah
          3. 2.18.2.4. readonly
          4. 2.18.2.5. skip
          5. 2.18.2.6. skip_jsdoc
          6. 2.18.2.7. start
          7. 2.18.2.8. main
          8. 2.18.2.9. typescript_custom_section
          9. 2.18.2.10. getter and setter
          10. 2.18.2.11. inspectable
          11. 2.18.2.12. skip_typescript
          12. 2.18.2.13. getter_with_clone
          13. 2.18.2.14. unchecked_return_type and unchecked_param_type
          14. 2.18.2.15. return_description and param_description
  6. 3. web-sys
    1. 3.1. Using web-sys
    2. 3.2. Cargo Features
    3. 3.3. Function Overloads
    4. 3.4. Type Translations
    5. 3.5. Inheritance
    6. 3.6. Unstable APIs
  8. 4. Testing with wasm-bindgen-test
    1. 4.1. Usage
    2. 4.2. Writing Asynchronous Tests
    3. 4.3. Testing in Headless Browsers
    4. 4.4. Continuous Integration
    5. 4.5. Coverage (Experimental)
  10. 5. Contributing to wasm-bindgen
    1. 5.1. Testing
  12. 5.2. Internal Design
    1. 5.2.1. JS Objects in Rust
      1. 5.2.2. Exporting a function to JS
      2. 5.2.3. Exporting a struct to JS
      3. 5.2.4. Importing a function from JS
      4. 5.2.5. Importing a class from JS
      5. 5.2.6. Rust Type conversions
      6. 5.2.7. Types in wasm-bindgen
  14. 5.3. js-sys
    1. 5.3.1. Testing
      1. 5.3.2. Adding More APIs
  16. 5.4. web-sys
    1. 5.4.1. Overview
      1. 5.4.2. Testing
      2. 5.4.3. Logging
      3. 5.4.4. Supporting More Web APIs
  18. 5.5. Publishing
  19. 5.6. Team

The `wasm-bindgen` Guide

Hello, World!

View full source code or view the compiled example online

This is the "Hello, world!" example of #[wasm_bindgen] showing how to set up a project, export a function to JS, call it from JS, and then call the alertfunction in Rust.

Cargo.toml

The Cargo.toml lists the wasm-bindgen crate as a dependency.

Also of note is the crate-type = ["cdylib"] which is largely used for wasm final artifacts today.

[package]
authors = ["The wasm-bindgen Developers"]
edition = "2021"
name = "hello_world"
publish = false
version = "0.0.0"

[lib]
crate-type = ["cdylib"]

[dependencies]
wasm-bindgen = { path = "../../" }

[lints]
workspace = true

src/lib.rs

Here we define our Rust entry point along with calling the alert function.


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

#[wasm_bindgen]
extern "C" {
    fn alert(s: &str);
}

#[wasm_bindgen]
pub fn greet(name: &str) {
    alert(&format!("Hello, {}!", name));
}

#}

index.js

Our JS entry point is quite small!

import { greet } from './pkg';

greet('World');

Webpack-specific files

Note: Webpack is required for this example, and if you're interested in options that don't use a JS bundler see other examples.

And finally here's the Webpack configuration and package.json for this project:

webpack.config.js

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const webpack = require('webpack');
const WasmPackPlugin = require("@wasm-tool/wasm-pack-plugin");

module.exports = {
    entry: './index.js',
    output: {
        path: path.resolve(__dirname, 'dist'),
        filename: 'index.js',
    },
    plugins: [
        new HtmlWebpackPlugin(),
        new WasmPackPlugin({
            crateDirectory: path.resolve(__dirname, ".")
        }),
    ],
    mode: 'development',
    experiments: {
        asyncWebAssembly: true
   }
};

package.json

{
  "scripts": {
    "build": "webpack",
    "serve": "webpack serve"
  },
  "devDependencies": {
    "@wasm-tool/wasm-pack-plugin": "1.5.0",
    "html-webpack-plugin": "^5.6.0",
    "webpack": "^5.97.0",
    "webpack-cli": "^5.1.4",
    "webpack-dev-server": "^5.0.4"
  }
}