js 时间戳运算

//第一种
var timestamp = Date.now();

//第二种
var timestamp = new Date().getTime();

//第三种
var timestamp = new Date().valueOf();

//第四种,通过运算
var timestamp = new Date() * 1; //new Date()-0 ,new Date()/1

//第五种 ,通过转换
var timestamp = Date.parse(new Date());

var timestamp1 = Date.now();
var timestamp2 = Date.now();
var timediff = (timestamp2 - timestamp1) / 1000; //这里拿到的是毫秒,除以1000 得到秒单位
//天数
var days = parseInt(timediff / 3600 / 24);

//小时
var hours = parseInt(timediff / 3600);

//分钟
var minutes = parseInt((timediff / 60) % 60);

//秒
var seconds = parseInt(timediff % 60);

function getDiff(t1, t2) {
  var timediff = (t2 - t1) / 1000;
  //天数
  var days = parseInt(timediff / 3600 / 24);
  //小时
  var hours = parseInt((timediff / 3600) % 60);
  //分钟
  var minutes = parseInt((timediff / 60) % 60);
  //秒
  var seconds = parseInt(timediff % 60);
  return days + "天 " + hours + "时 " + minutes + "分 " + seconds + "秒 ";
}

var t1 = new Date("2019/2/10 8:03:15");
var t2 = new Date("2019/2/18 7:05:55");

var result = getDiff(t1, t2);

console.log(result);
//7天 11时 2分 40秒

//开始倒计时 今天离2025年还有多少天
setInterval(
  () => console.log(getDiff(new Date(), new Date("2025/3/20"))),
  1000
);