一段倒计时的js代码

window.onload = function(){
    function countTime(){
        //获取当前时间
        var date = new Date();
        var now = date.getTime();
        //设置截止时间
        var endDate = new Date("10/10/2018");
        var end = endDate.getTime();
        //时间差
        var leftTime = end-now;
        //定义变量 d,h,m,s保存倒计时的时间
        var d,h,m,s;
        if (leftTime>=0) {
            d = Math.floor(leftTime/1000/60/60/24);
            h = Math.floor(leftTime/1000/60/60%24);
            m = Math.floor(leftTime/1000/60%60);
            s = Math.floor(leftTime/1000%60);
        }
        //将倒计时赋值到div中
        document.getElementById("day").innerHTML = d;
        document.getElementById("hour").innerHTML = h;
        document.getElementById("minute").innerHTML = m;
        document.getElementById("seconds").innerHTML = s;
    }
    setInterval(countTime,1000);
}