最近经常碰到页面活动倒计时的效果，于是写了个js倒计时的方法，独立出来成js文件，以后用到直接引用Common.js文件就可以了。很简单的js，记一下：

Common.js文件：

var CountDown = {
        "LeftTime": function (t) { //t参数格式 : 2015/2/11 10:08:51        var dt = new Date(t);        var now = new Date();        var disTime = dt - now;        if (disTime <= 0) {            return 0;        }        var days = parseInt(disTime / (1000 * 3600 * 24));        var leftDay = parseInt(disTime % (1000 * 3600 * 24));        var hours = parseInt(leftDay / (1000 * 3600));        var leftHour = parseInt(leftDay % (1000 * 3600));        var minutes = parseInt(leftHour / (1000 * 60));        var leftMinute = parseInt(leftHour % (1000 * 60));        var seconds = parseInt(leftMinute / (1000));        var showDay = (days < 10) ? ('0' + days.toString()) : days.toString();        var showHour = (hours < 10) ? ('0' + hours.toString()) : hours.toString();        var showMinute = (minutes < 10) ? ('0' + minutes.toString()) : minutes.toString();        var showSecond = (seconds < 10) ? ('0' + seconds.toString()) : seconds.toString();        return showDay + "|" + showHour + "|" + showMinute + "|" + showSecond;    }};

下面是不能实现倒计时的：

var CountDown = {    "now": new Date(), // CountDown对象创建的时候，now成员变量只赋一次值    "LeftTime": function (t) { //t参数格式 : 2015/2/11 10:08:51        var dt = new Date(t);        var now = this.now; // 获取的now属性的值是不变的，所以倒计时不会真正的倒计时        var disTime = dt - now;        if (disTime <= 0) {            return 0;        }        var days = parseInt(disTime / (1000 * 3600 * 24));        var leftDay = parseInt(disTime % (1000 * 3600 * 24));        var hours = parseInt(leftDay / (1000 * 3600));        var leftHour = parseInt(leftDay % (1000 * 3600));        var minutes = parseInt(leftHour / (1000 * 60));        var leftMinute = parseInt(leftHour % (1000 * 60));        var seconds = parseInt(leftMinute / (1000));        var showDay = (days < 10) ? ('0' + days.toString()) : days.toString();        var showHour = (hours < 10) ? ('0' + hours.toString()) : hours.toString();        var showMinute = (minutes < 10) ? ('0' + minutes.toString()) : minutes.toString();        var showSecond = (seconds < 10) ? ('0' + seconds.toString()) : seconds.toString();        return showDay + "|" + showHour + "|" + showMinute + "|" + showSecond;    }};

使用的页面：

Index

 在使用的页面使用计时器，就可以实现页面倒计时效果了。

Index

 

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附加js面向对象知识：

//第1种写法      function Circle(r) {            this.r = r;      }      Circle.PI = 3.14159;      Circle.prototype.area = function() {        return Circle.PI * this.r * this.r;      }            var c = new Circle(1.0);         alert(c.area());

//第2种写法      var Circle = function() {         var obj = new Object();         obj.PI = 3.14159;                  obj.area = function( r ) {             return this.PI * r * r;         }         return obj;      }            var c = new Circle();      alert( c.area( 1.0 ) );

//第3种写法      var Circle = new Object();      Circle.PI = 3.14159;      Circle.Area = function( r ) {             return this.PI * r * r;      }            alert( Circle.Area( 1.0 ) );

//第4种写法      var Circle={         "PI":3.14159,       "area":function(r){                return this.PI * r * r;              }      };      alert( Circle.area(1.0) );

//第5种写法      var Circle = new Function("this.PI = 3.14159;this.area = function( r ) {return r*r*this.PI;}");            alert( (new Circle()).area(1.0) );

特别是最后两种，经常见到。