JavaScript 学习三 继承

//继承第一种方式：对象冒充/*function Parent(username){this.username = username;this.hello = function(){alert(this.username);}}function Child(username, password){this.method = Parent;this.method(username);//最关键的一行delete this.method;//Parent(username);this.password = password;this.world = function(){alert(this.password);}}var parent = new Parent("zhangsan");var child = new Child("lisi", "123456");parent.hello();child.hello();child.world();*///继承第二种方式：call()方法方式/*function test(str){alert(this.name + " " + str);}var object = new Object();object.name = "zhangsan";test.call(object,"langsin");function Parent(username){this.username = username;this.hello = function(){alert(this.username);}}function Child(username, password){Parent.call(this,username);this.password = password;this.world = function(){alert(this.password);}}var parent = new Parent("zhangsan");var child = new Child("lisi", "123456");parent.hello();child.hello();child.world();*///继承第二种方式：apply()方法方式function Parent(username){this.username = username;this.hello = function(){alert(this.username);}}function Child(username, password){Parent.apply(this,new Array(username));this.password = password;this.world = function(){alert(this.password);}}var parent = new Parent("zhangsan");var child = new Child("lisi", "123456");parent.hello();child.hello();child.world();/*//原型链function Parent(){}Parent.prototype.hello = "hello";Parent.prototype.sayHello = function(){alert(this.hello);}function Child(){}Child.prototype = new Parent();Child.prototype.world = "world";Child.prototype.sayWorld = function(){alert(this.world);}var child = new Child();child.sayHello();child.sayWorld();//混合方式function Parent(hello){this.hello = hello;}Parent.prototype.sayHello = function(){alert(this.hello);}function Child(hello, world){Parent.call(this, hello);this.world = world;}Child.prototype = new Parent();Child.prototype.sayWorld = function(){alert(this.world);}var child = new Child('hello', 'world');child.sayHello();child.sayWorld();*/function Shape(edge){this.edge = edge;}Shape.prototype.getArea = function(){return -1;}Shape.prototype.getEdge = function(){return this.edge;}function Triangle(bottom, height){Shape.call(this, 3);this.bottom = bottom;this.height = height;}Triangle.prototype = new Shape();Triangle.prototype.getArea = function(){return 0.5 * this.bottom * this.height;}/*Triangle.prototype.getEdge = function(){return this.edge;}*/var triangle = new Triangle(10,4);alert(triangle.getEdge()); // 3alert(triangle.getArea()); // 20function Rectangle(bottom, height){Shape.call(this, 4);this.bottom = bottom;this.height = height;}Rectangle.prototype = new Shape();Rectangle.prototype.getArea = function(){return this.bottom * this.height;}/*Rectangle.prototype.getEdge = function(){return this.edge;}*/var rectangle = new Rectangle(10,20);alert(rectangle.getEdge()); //4alert(rectangle.getArea()); //200