JavaScript 类、构造函数、原型

 1 //类 构造函数  原型对象  this代表调用对象 
 2 function R(w, h) {
 3     var date = new Date();
 4     this.width = w;
 5     this.height = h;
 6     this.createtime = date.getFullYear() + "-" + date.getMonth() + "-" + date.getDay() + " " + date.getHours() + ":" + date.getMinutes() + ":" + date.getSeconds();
 7 
 8 }
 9 R.prototype.area = function () {
10     return this.width * this.height;
11 }
12 var o = new R(10, 20);
13 console.log(o.createtime + ":" + o.area());

 1 //类 构造函数  原型对象  this代表调用对象
 2 function R(w, h) {
 3     var date = new Date();
 4     this.width = w;
 5     this.height = h;
 6     this.createtime = date.getFullYear() + "-" + date.getMonth() + "-" + date.getDay() + " " + date.getHours() + ":" + date.getMinutes() + ":" + date.getSeconds();
 7     R.count++;
 8 }
 9 R.prototype.area = function () {
10     return this.width * this.height;
11 }
12 //以上创建的都是实例属性和实例方法,以下为类属性和类方法
13 R.count = 0;
14 R.getCount = function () {
15     return R.count;
16 }
17 
18 var o = new R(10, 20);
19 console.log("createtime:" + o.createtime + "\narea:" + o.area() + "\nR.count=" + R.getCount());
20 var o2 = new R(20, 30);
21 console.log("createtime:" + o2.createtime + "\narea:" + o2.area() + "\nR.count=" + R.getCount());

 1 //私有属性(只能通过专门的方法才能读取和写入),使用了闭包原理，因为里面定义的函数被外部的全局对象引用了，
 2 //外部函数的调用对象不会被释放，w 和 h值一直维持最近一次的值，并且直到外部的引用消失，才会被释放内存
 3 function R(w, h) {
 4     this.getWidth = function () {
 5         return w;
 6     }
 7     this.getHeight = function () {
 8         return h;
 9     }
10     this.setWidth = function (width) {
11         w = width;
12     }
13     this.setHeight = function (height) {
14         h = height;
15     }
16 }
17 var o = new R(10, 20);
18 alert(o.getWidth() * o.getHeight());
19 o.setWidth(100);
20 o.setHeight(200);
21 alert(o.getWidth() * o.getHeight());