javascript继承

拷贝继承

 1 　　 function Foo(){   //父类
 2         this.name = 'hello';
 3     }
 4     Foo.prototype.showName = function(){
 5         console.log(this.name);
 6     };
 7     function Bar(){   //子类
 8         Foo.call(this);
 9         this.age = 20;
10         this.name = 'hi'
11     }
12     extend(Bar,Foo);
13     Bar.prototype.showAge = function(){
14         console.log(this.age);
15     };
16     function extend(subs,sups){
17         for(var attr in sups.prototype){
18             subs.prototype[attr] = sups.prototype[attr];
19         }
20     }
21     var obj1 = new Foo();
22     var obj2 = new Bar();
23     console.log(obj1);
24     console.log(obj2);
25     obj2.showName()

类式继承

 1     function Foo(){
 2         this.name = 'hello';
 3     }
 4     Foo.prototype.showName = function(){
 5         console.log(this.name);
 6     };
 7     function Bar(){
 8         Foo.call(this);
 9         this.age = 20;
10     }
11     extend(Bar,Foo);
12     Bar.prototype.showAge = function(){
13         console.log(this.age);
14     };
15     function extend(subs,sups){
16         var F = function(){};
17         F.prototype = sups.prototype;
18         subs.prototype = new F();
19     // constructor 找对应的构造函数;
20         subs.prototype.constructor = subs;
21     }
22     var obj1 = new Foo();
23     var obj2 = new Bar();
24     console.log(obj1);
25     console.log(obj2);

非构造函数拷贝继承

 1     var foo = {
 2         name : 'hello'
 3     };
 4     foo.showName = function(){
 5         console.log(this.name)
 6     }
 7     var bar = extend(foo);
 8     function extend(sups){
 9         var result = {};
10         for(var attr in sups){
11             result[attr] = sups[attr];
12         }
13         return result;
14     }
15     console.log(bar);
16     bar.name = 'hi';
17     console.log(bar);
18     console.log(foo);
19     bar.showName();

原型链形式

 1 　　 var foo = {
 2         name : 'hello',
 3         showName: function(){
 4             console.log(this.name)
 5         }
 6     };
 7     var bar = extend(foo);
 8     function extend(sups){
 9         function F() {}
10         F.prototype = sups;
11 　　　　return new F();
12     }
13     console.log(bar);
14     bar.name = 'hi';
15     console.log(bar);
16     console.log(foo);
17     bar.showName()