用原生实现了一个简单的倒计时，主要用到setInterval来控制时间100%至0%，当进度为0%时，clearInterval，然后在时间小于某个值时，小小改变了倒计时的填充颜色，当然了这只是一个雏形，可根据实际需要进行封装
附源码：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> <style type="text/css"> .timeContainer{ width: 200px; height: 30px; border-radius: 6px; border: 1px solid #ccc; } .timeContainer #countDown{ height:100%; background: orange; } </style> </head> <body>倒计时: <div class="timeContainer"> <div id="countDown" style=" 100%;"></div> </div> <script type="text/javascript"> window.onload = function () { myTime } function countDown () { let timeCount = document.getElementById('countDown') timeCount.style.width = parseInt(timeCount.style.width) - 1 + '%' if (timeCount.style.width < '30%') { timeCount.style.background = 'red' } if (timeCount.style.width == '0%') { window.clearInterval(myTime) } } let myTime = setInterval(function() {countDown()}, 100) </script> </body> </html>