javascript实现sleep函数，不堵塞线程

通过Promise实现sleep函数，区别于循环，不堵塞线程

function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

async function test() {
  console.log('start test.');
  await sleep(3000);
  console.log('end test.');
}

test();
console.log('continue execute！');