>[success] # js 倒計時 制作倒計時思路就是將**setTimeout** 通過**promise**進行包裹，利用while 循環去持續調用封裝好的倒計時 ~~~ // 異步倒計時 function wait(ms) { return new Promise((res) => { setTimeout(res, ms) }) } // 倒計時執行方法 async function starting(el, count = 3) { while (count--) { await wait(1000) el.innerText = count } el.innerText = '' } // 使用時候 const startingEl = document.getElementById('starting') starting(startingEl ) ~~~ * 時分秒倒計時 ~~~ async function countDown(el, sec) { while(sec--) { const minute = Math.floor(sec / 60); const second = sec % 60; const time = `${minute > 10 ? minute: `0${minute}`}:${second > 10 ? second: `0${second}`}`; el.innerText = time; await wait(1000); } } ~~~