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AssemblyScript

Build WebAssembly with TypeScript-like syntax using AssemblyScript.

Overview​

AssemblyScript is a TypeScript-like language that compiles to WebAssembly. The wasmasc plugin provides seamless integration with Wasmrun.

Prerequisites​

  • Node.js 16 or higher
  • npm, yarn, pnpm, or bun (package manager)
  • wasmrun installed (see Installation)

Plugin Installation​

wasmrun plugin install wasmasc

Quick Start​

# Create project
mkdir my-asc-wasm && cd my-asc-wasm
npm init -y

# Install AssemblyScript
npm install --save-dev assemblyscript

# Initialize AssemblyScript
npx asinit .

# Edit assembly/index.ts
cat > assembly/index.ts << 'EOF'
export function add(a: i32, b: i32): i32 {
  return a + b;
}

export function greet(name: string): string {
  return `Hello, ${name}!`;
}
EOF

# Run with Wasmrun
wasmrun run . --watch

Project Structure​

my-asc-wasm/
├── assembly/
│   ├── index.ts      # Source code
│   └── tsconfig.json # TypeScript config
├── build/            # Compiled output
├── package.json
└── asconfig.json     # AssemblyScript config

Type System​

AssemblyScript uses WebAssembly types:

// Integer types
let a: i32 = 42;        // 32-bit integer
let b: i64 = 100n;      // 64-bit integer
let c: u32 = 255;       // unsigned 32-bit
let d: u8 = 8;          // unsigned 8-bit

// Float types
let e: f32 = 3.14;      // 32-bit float
let f: f64 = 2.71828;   // 64-bit float

// Boolean and strings
let g: bool = true;
let h: string = "Hello";

Exported Functions​

// Export for JavaScript
export function fibonacci(n: i32): i32 {
  if (n <= 1) return n;
  return fibonacci(n - 1) + fibonacci(n - 2);
}

export function processArray(arr: Int32Array): i32 {
  let sum: i32 = 0;
  for (let i = 0; i < arr.length; i++) {
    sum += arr[i];
  }
  return sum;
}

Examples​

Simple Functions​

See examples/asc-hello

Web Application​

See examples/web-asc

Optimization​

{
  "options": {
    "optimize": true,
    "optimizeLevel": 3,
    "shrinkLevel": 2,
    "converge": true
  }
}

Best Practices​

  1. Use specific integer types (i32, i64) instead of number
  2. Avoid dynamic arrays when possible
  3. Use typed arrays for performance
  4. Enable optimizations for production builds

Additional Resources​