AssemblyScript

AssemblyScript is a TypeScript-like language designed specifically for Wasm. It has static types (i32, f64, u8...), compiles via Binaryen, produces small output, and has a familiar syntax for web developers.

Features: generics, classes, closures (limited), memory management runtimes (incremental GC, minimal, stub), SIMD (v128), load<T>/store<T> intrinsics, @inline, unchecked().

Differences from TypeScript: no any/union types (except nullable), no dynamic objects, integer types matter, and a limited stdlib.

npm init -y
npm install --save-dev assemblyscript
npx asinit .

// assembly/index.ts
export function add(a: i32, b: i32): i32 {
  return a + b;
}

export function fib(n: i32): i64 {
  let a: i64 = 0, b: i64 = 1;
  for (let i = 0; i < n; i++) {
    const t = a + b;
    a = b;
    b = t;
  }
  return a;
}

export function sumArray(arr: Float64Array): f64 {
  let total = 0.0;
  for (let i = 0; i < arr.length; i++) total += unchecked(arr[i]);
  return total;
}

export function greet(name: string): string {
  return "Hello, " + name + "!";
}

@external("env", "logValue")
declare function logValue(v: f64): void;

export class Vec2 {
  constructor(public x: f64, public y: f64) {}
  length(): f64 { return Math.sqrt(this.x * this.x + this.y * this.y); }
}

npm run asbuild          # builds build/debug.wasm and build/release.wasm + JS bindings (--bindings esm)

import { add, greet, sumArray } from "./build/release.js";
console.log(add(1, 2), greet("Ana"), sumArray(new Float64Array([1, 2, 3])));