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js继承的几种方式

原型链继承:无法传参

function Fun1(){

  this.property = true;

}

Fun1.prototype.getValue = function(){

  return this . property;

}

Function Fun2(){

  this.sub = false;

}

Fun2.prototype = new Fun1();

Fun2.prototype .sayValue = function(){

  return this.sub;

}

Var instance = new Fun2();

Console.log(instance.getValue());

// 创建Fun1的实例,并讲该实例赋给Fun2.prototype实现的。本质是重写原型对象,代之以一个新类型的实例。原来存在于Fun1的实例中的属性和方法,现在也存在于Fun2.prototype中了。

 

构造函数call() apply()  解决传参的问题,父类原型的属性和方法不能继承,实例不是父类的实例

function Fun1(){

  this.color=[‘red’ , ’blue’];

}

function Fun2(){

  fun1.call(this);

}

var instance1 = new Fun2();

Instance1.colors.push(“black”);

Console.log(instance1.colors); //red blue black

 

Var instance2 = new Fun2();

Console.log(instance2.colors); // red blue

 

传参:

Function Fun1(name){

  this.name = name;

}

Function Fun2(age){

Fun2.call(this, “John”);

  This.age = 23;

}

Var instance = new Fun2();

Console.log(instance.name)// John

Console.log(instance.age)//23

 

 

组合继承:组合原型链和构造函数,原型链实现对原型属性和方法的继承,构造函数来实现对实例属性的继承。

Function Fun1(name){

This.name = name;

This.color = [“red” , “blue”];

}

Fun1.prototype.sayName = function(){

alert(this.name);

}

Function Fun2(name , age){

Fun1.call(this , name);

This.age = age;

}

Fun2.prototype = new Fun1();

Fun2.prototype.sayAge = function(){

Console.log(this.age);

}

Var instance1= new Fun2(“John”, 29);

Instance1.colors.push(“black”);

Console.log(instance1.colors); //red blue black

Instance1.sayName (); //John

Instance1.sayAge(); // 29

 

Var instance2 = new Fun2();

Console.log(Instance2.color); //red blue

Instance.sayName();//John

Instance.sayAge(); //29

 

原型式继承:借助原型可以基于已有的对象创建新对象,同时还不必须因此创建自定义的类型。

 

//新增Object.create()方法规范了原型式继承
//可以传递两个参数,第一个是用作新对象原型的对象,第二个(可选)为新对象定义额外属性的对象

//传递一个参数时,等同于object()
var person = {
  name:"EvanChen",
  friends:["Shelby","Court","Van"];
};
 var anotherPerson = Object.create(person);
anotherPerson.name = "Greg";
anotherPerson.friends.push("Rob");
 
var yetAnotherPerson = Object.create(person);
yetAnotherPerson.name = "Linda";
yetAnotherPerson.friends.push("Barbie");
 
console.log(person.friends);//"Shelby","Court","Van","Rob","Barbie"
思想:

function object(o) {

  function F(){ }

  F.prototype = o;

  return new F();

}

var person = {
    name:"EvanChen",
    friends:["Shelby","Court","Van"];
};
var anotherPerson = object(person);
anotherPerson.name = "Greg";
anotherPerson.friends.push("Rob");

var yetAnotherPerson = object(person);
yetAnotherPerson.name = "Linda";
yetAnotherPerson.friends.push("Barbie");

console.log(person.friends);//"Shelby","Court","Van","Rob","Barbie"
//必须有一个对象作为另一个对象的基础,如果有这么一个对象的话,可以传递给object()函数,然后该函数就会返回一个新的对象

posted on 2018-03-16 11:52  一只大鸡腿  阅读(212)  评论(0编辑  收藏  举报