Handling Binary Data

const buf = new ArrayBuffer(16);
const u8 = new Uint8Array(buf);
u8.set([1,2,3,4]);

const v = new DataView(buf);
v.setUint32(0, 0xCAFEBABE, false);   // big-endian
const n = v.getUint32(0, false);
const f = v.getFloat32(4, true);     // little-endian

ws.binaryType = "arraybuffer";
ws.onmessage = (e) => {
  const view = new DataView(e.data);
  const opcode = view.getUint8(0);
  dispatch(opcode, view);
};

// frame: [u8 type][u16 len][len bytes value]
function frame(type, value) {
  const out = new Uint8Array(3 + value.length);
  out[0] = type;
  new DataView(out.buffer).setUint16(1, value.length, false);
  out.set(value, 3);
  return out.buffer;
}