JavaScript 倒计时案例

<script>        
    setInterval(function () {        // setInterval 是一个计时器  按照给定的时间每秒刷新
        let now = new Date()         //  获取现在的时间 
        let time= new Date('2020-08-31 19:00:00')         
        let sec = (time - now) / 1000           
        let h = Math.floor(sec / (60 * 60))            
        let m = Math.floor(sec % (60 * 60) / 60)            
        let s = Math.floor(sec % (60 * 60) % 60)           
        h = h < 10 ? '0' + h : h            
        m = m < 10 ? '0' + m : m            
        s = s < 10 ? '0' + s : s            
        console.log([h, m, s].join(':'));        
   }, 1000)    
</script>