assemblyscript/tests/compiler/game-of-life.html

<canvas id="canvas" width="640" height="480"></canvas>
<script src="../../node_modules/binaryen/index.js"></script><script>

// Fetch the .wast (just because we dont's store the .wasm in git)
fetch("game-of-life.optimized.wast").then(response => response.text()).then(text => {

  // Convert it to binary format
  var binary = Binaryen.parseText(text).emitBinary();

  // Instantiate the module
  var module = new WebAssembly.Module(binary);
  var instance = new WebAssembly.Instance(module, { /* no imports */ });

  // Set up the canvas with a 2D rendering context
  var cnv = document.getElementById("canvas");
  var ctx = cnv.getContext("2d");
  var w = cnv.width,
      h = cnv.height,
      s = w * h, // memory required to store either input or output
      S = s + s; // total memory required to store input and output

  // Grow the (exported) memory if its size isn't sufficient
  var memory = instance.exports.memory;
  if (memory.buffer.byteLength < S)
    memory.grow(Math.ceil((S - memory.buffer.byteLength) / 65536));

  // Initialize with width and height
  instance.exports.init(w, h);

  // Fill input at [0, s-1] with random live cells
  var mem = new Uint8Array(memory.buffer);
  for (var y = 0; y < h; ++y)
    for (var x = 0; x < w; ++x)
      mem[y * w + x] = Math.random() > 0.1 ? 0 : 1;

  // Update about 30 times a second
  (function update() {
    setTimeout(update, 33);
    instance.exports.step();
    mem.set(mem.subarray(s, S), 0); // copy output -> input
  })();

  // Keep rendering the output at [s, 2*s-1]
  (function render() {
    requestAnimationFrame(render);
    ctx.clearRect(0, 0, w, h);
    ctx.fillStyle = "#333";
    for (var y = 0; y < h; ++y)
      for (var x = 0; x < w; ++x)
        if (mem[s + y * w + x])
          ctx.fillRect(x, y, 1, 1);
  })();

}).catch(err => {
  throw err;
});
</script>