日期对象

##算出从出生到现在活了多少天

```

        var now=new Date('2001/07/11 10:00:10');

        var old=new Date();

        var day=old-now;

        var days=day/1000/60/60/24;

        console.log(day);

        console.log(days);

##日期对象API

```

         年：FullYear

        月：Month

        日：Date

        星期：Day

        小时：Hours

         分钟: Minutes

          秒: Seconds

         毫秒:Millseconds

```

##一次性定时器 永久性定时器

```

        setTimeout(function(){},毫秒数)

         var timer=setTimeout(function(){

                console.log(1111);         延迟3000毫秒执行一次

         },3000)

        btn1.onclick=function(){.

                clearTimeout(timer);    停止一次性定时器

         }

···

##永久性定时器+案例

```

        var a=setInterval(function(){

        var now=new Date();

        年

        var year=now.getFullYear();

          console.log(year);

        月

        var month=now.getMonth();

        console.log(month);

        日

          var dates=now.getDate();

        console.log(dates);

        星期

        var day=now.getDay();

        console.log(day);

        小时

        var hours=now.getHours();

        console.log(hours);

        分钟

          var min=now.getMinutes();

        console.log(min);

        秒

       var sec=now.getSeconds();

        console.log(sec);

        document.querySelector('div').innerHTML='北京时间:'+year+'年'+month+'月'+dates+'日,         星  期'+day + hours+'小时'+min+'分钟'+sec+'秒';},1000)

        btn1.onclick=function(){

        clearInterval(a);

          }

```