js如何利用setTimeout实现倒计时

如何利用js​语法中setTimeout()函数做一个倒计时功能，下面web建站小编给大家详细介绍一下具体代码！

步骤一：获取具体时间

function myData(){
  var year = document.getElementById("year").value;
  var month = document.getElementById("month").value-1;
  var day = document.getElementById("day").value;
  var hour = document.getElementById("hour").value;
  var minute = document.getElementById("minute").value;
  var second = document.getElementById("second").value;
  var time = Number(new Date(year, month, day, hour, minute, second));
}

步骤二：获取时间差

//获取当前时间
var nowTime = Date.now();

//获取时间差
var timediff = Math.round((time-nowTime) / 1000);

步骤三：时间转换

//获取还剩多少天
var day = parseInt(timediff / 3600 / 24);

//获取还剩多少小时
var hour = parseInt(timediff / 3600 % 24);

//获取还剩多少分钟
var minute = parseInt(timediff / 60 % 60);

//获取还剩多少秒
var second = timediff % 60;

步骤四：输出剩余时间

document.getElementById("d").innerHTML = day;
document.getElementById("h").innerHTML = hour;
document.getElementById("m").innerHTML = minute;
document.getElementById("s").innerHTML = second;

步骤五：倒计时输出

var set = setTimeout(show,1000);
if(timediff == 0){
  clearInterval(set);
}