JavaScript Date对象实战：实时时钟、高考倒计时与限时抢购

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>date01</title>
  <style>
    #date{
      position: absolute;
      font-size: 30px;
      font-family: '微软雅黑';
      top:50%;
      left:50%;
      -webkit-transform:translate(-50%,-50%);
    }
  </style>
</head>
<body>
  <div id="date">2017.10.29</div>
  <script>
    window.onload = function(){
      showTime();
    }
    //checkTime(i)对分钟和秒进行判断，如果小于10，在其前补0.
    function checkTime(i){
      return i < 10? "0"+i:i;
    }
    function showTime(){
      var time = new Date();//日期对象
      console.log("new Date :"+time);
      var year_1 = time.getYear();//获得年份
      console.log("getYear(): "+year_1);
      var year_2 = time.getFullYear();//获得完整年份
      console.log("getFullYear(): "+year_2);
      var month = time.getMonth();//获得月份(0~11)
      console.log("getMonth(): "+month);
      var date = time.getDate();//获得日期(1~31)
      console.log("getDate(): "+date);
      var day = time.getDay();//星期几(0~6)
      console.log("getDay(): "+day)
      var hours = time.getHours();//小时(0~23)
      console.log("getHours(): "+hours);
      var min = time.getMinutes();//分钟(0~59)
      console.log("getMinutes(): "+min);
      var seconds = time.getSeconds();//秒
      console.log("getSeconds(): "+seconds);

      min = checkTime(min);
      seconds = checkTime(seconds);

      var weekday = new Array(7);
      weekday[0] = "星期天"; 
      weekday[1] = "星期一";
      weekday[2] = "星期二";
      weekday[3] = "星期三";
      weekday[4] = "星期四";
      weekday[5] = "星期五";
      weekday[6] = "星期六";

      var str_time = year_2 + "年" + (month+1) + "月" + date + "日" +" "+ weekday[day] +" "+ hours +":" + min +":" + seconds;

      document.getElementById('date').innerHTML = str_time;
      setTimeout(showTime,500);//每500ms执行一次，实现秒数实时跳动。
    }  
    
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>date02</title>
  <style>
    #date{
      position: absolute;
      font-size: 30px;
      font-family: '微软雅黑';
      top:50%;
      left:50%;
      -webkit-transform:translate(-50%,-50%);
    }
  </style>
</head>
<body>
  <div id="date">2017.10.29</div>
  <script>
    window.onload = function(){
      var now = new Date();//获取当前时间
      var timedate = new Date("2018,12,23");//截止时间
      //getTime() 方法可返回距 1970 年 1 月 1 日之间的毫秒数。
      var date = timedate.getTime() - now.getTime();
      //Math.ceil()向上取整
      var time = Math.ceil(date/(24*60*60*1000));
      document.getElementById('date').innerHTML = time;

    }
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>date03</title>
  <style>
    #date{
      position: absolute;
      font-size: 30px;
      font-family: '微软雅黑';
      top:50%;
      left:50%;
      -webkit-transform:translate(-50%,-50%);
    }
  </style>
</head>
<body>
  <div id="date">2017.10.29</div>
  <script>
    window.onload = function(){
      showTime();

    }
    function checkTime(i){
      return i < 10? "0"+i:i;
    }
    function showTime(){
      var now = new Date();//获取当前时间
      var timedate = new Date("2017/10/30,24:00:00");//截止时间
      //getTime() 方法可返回距 1970 年 1 月 1 日之间的毫秒数。
      var leftTime = (timedate.getTime() - now.getTime())/1000;
      var d = checkTime(parseInt(leftTime/(24*60*60)));
      var h = checkTime(parseInt(leftTime/(60*60)%24));
      var m = checkTime(parseInt(leftTime/60%60));
      var s = checkTime(parseInt(leftTime%60));
      var time = d + "天" + h + "小时" + m + "分钟" + s + "秒";
      document.getElementById('date').innerHTML = time;
      setTimeout(showTime,500);
    }
  </script>
</body>
</html>