Function asyncOnMessageWrap

ch2-patterns/worker.js:3–7

(fn)

const sleep = (ms) => new Promise((res) => setTimeout(res, ms)); // <1>

function asyncOnMessageWrap(fn) { // <2>
  return async function(msg) {
    postMessage(await fn(msg.data));
  }
}

const commands = {
  async square_sum(max) {