Hello WebAssembly

Introduction

WebAssembly (Wasm) lets you run compiled code in the browser at near-native speed. Rust is one of the best languages for targeting Wasm because of its zero-cost abstractions, no garbage collector, and small binary sizes.

How It Works

1. You write Rust code and annotate functions with #[wasm_bindgen]
2. The wasm-pack tool compiles your Rust code to a .wasm binary
3. JavaScript can import and call your exported functions directly

Key Concepts

• #[wasm_bindgen] — marks functions to be accessible from JavaScript
• &str — Rust's string slice type, automatically converted from JS strings
• Return types — Rust types like String, i32, f64 are converted to JS equivalents

Calling from JavaScript

Once compiled with wasm-pack, you can import and call your Rust functions directly:

import init, { greet, add } from './pkg/hello_wasm.js';

async function run() {
    await init();
    console.log(greet("World"));
    console.log("2 + 3 =", add(2, 3));
}
run();

Try It

Modify the greet function to include a personalized message, or add a new exported function like multiply.