js实现sleep休眠

const sleep = ms =>{
  return new Promise((res,rej)=>{
    setTimeout(res,ms);
  })
}

sleep(2000).then(()=>{
    alert("延时2s")
})

优化版

const delay = ms =>{
  return new Promise((res,rej)=>{
    setTimeout(res,ms);
  })
}

async function sleep(ms) {
  await delay(ms);
}
sleep(2000).then(() => {
  console.log("延时2s")
})