<body>
    <div id="we">4</div>s
    <script>
    window.onload = function(){
        var we = document.getElementById("we")
        console.log(we.innerHTML);
       var int=setInterval(function(){
            we.innerHTML--;
            if(we.innerHTML==0){
                clearInterval(int);
            }
        },1000);
    }
</script>
</body>
就这么点东西。
 
        