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类方法与对象方法

2024-08-13 09:19:20   222人阅读

js函数式编程确实比很多强语言使用灵活得多，今天抽了点时间玩下类与对象方法调用优先级别，顺便回顾下继承

暂时把原型引用写成继承

 

先看看简单的两个继承

var Parent = function(){};var b = new  Parent();Object.defineProperty(b,"Name",{value:"John",writable:true});var A = function(){};A.prototype= b;var a = new Child();alert(a.Name); //John

 

再加点料，给父类加上类方法

var B = function(){this.getName=function(){};var b = new B();Object.defineProperty(b,"Name",{value:"John",writable:true});B.prototype.getName = function(){return "Parent said:" + this.Name;};
B.prototype.setName = function(value){this.Name = value;};var A = function(){};A.prototype= b;var a = new A();alert(a.Name); // Parent said Johnalert(a.getName()); //Parent said John
a.setName("Keven");
alert(a.getName());//Parent said Keven

 

子类继承并使用了父类原型的方法和属性, 也能通过父类提供的方法修改继承的属性值，再来加点料

 

var Parent = function(){this.getName=function(){return "Parent child object said:"+this.Name};};var b = new Parent();Object.defineProperty(b,"Name",{value:"John",writerable:true});Parent.prototype.getName = function(){return "Parent sard:" + this.Name;};Parent.prototype.setName = function(value){this.Name = value;};var A = function(){};A.prototype= b;var a = new A();
alert(a.Name); // Parent said Johnalert(a.getName()); //Parent said John
a.setName("Keven");
alert(a.getName());//Parent child object said John

What, 最后一条输出没有出来Keven, 而是调用了对象的方法，此处可以看出对象方法优先于原型方法调用，当对象方法没有找到时会向上层原型查找

 

再来看看类方法，再来加点料，Parent类加上getName方法，胃口有点重

var Parent = function(){this.getName=function(){return "Parent child object said:"+this.Name};};var b = new Parent();Object.defineProperty(b,"Name",{value:"John",writerable:true});Parent.prototype.getName = function(){return "Parent sard:" + this.Name;};Parent.getName = fucntion(){return this.Name;};Parent.prototype.setName = function(value){this.Name = value;};var A = function(){};A.prototype= b;var a = new A();alert(a.Name); // Parent said Johnalert(a.getName()); //Parent said Johna.setName("Keven");alert(a.getName());//Parent child object said Kevenalert(A.prototype.Name); //John
alert(A.getName()) // type error, undefine is not a function

最后一条报错，A并没有继承Parent的getName方法，此处可以理解Parent.getName为静态方法，不会被子类继承

var Parent = function(){this.getName=function(){return "Parent child object said:"+this.Name};};var b = new Parent();Object.defineProperty(b,"Name",{value:"John",writerable:true});Parent.prototype.getName = function(){return "Parent sard:" + this.Name;};Parent.getName = fucntion(){return this.Name;};Parent.prototype.setName = function(value){this.Name = value;};var A = function(){this.getName=function(){return "A object said:"+this.Name};};A.prototype= b;var a = new A();alert(a.Name); // Parent said Johna.setName("Keven");alert(a.getName());//A object said Kevenalert(A.prototype.Name); //Johnalert(A.getName()) // type error, undefine is not a function

　　

 

类方法与对象方法


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