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理解js对象继承的N种模式

  作者：bea

本文分享了js对象继承的N种模式，供大家参考。 一、原型链继承 function Person(){};Person.prototype = { constructor: Person, name: "Oliver"}; function People(){};People.prototype = new Person();People.prototype.constructor = People;People.prototype.sayName = funct

本文分享了js对象继承的N种模式，供大家参考。


一、原型链继承




function Person(){};



Person.prototype = {

  constructor: Person,

  name: "Oliver"

};

    

function People(){};



People.prototype = new Person();

People.prototype.constructor = People;

People.prototype.sayName = function(){

  return this.name;

};



var ins = new People();



console.log(ins.sayName());


二、借用构造函数（伪造对象，经典继承）


1、无参数




function SuperType(){

  this.color = ["red","yellow","white"];

}

function SubType(){

  SuperType.call(this);

}



var instance1 = new SubType();

var instance2 = new SubType();



instance1.color.pop();

console.log(instance1.color); //["red", "yellow"]

console.log(instance2.color); //["red", "yellow", "white"]


2、有参数




function SuperType(name){

  this.name = name;

  this.number = [21,32,14,1];

}

function SubType(name,age){

  SuperType.call(this,name);

  this.age = age;

}



var instance1 = new SubType("Oliver",18);

var instance2 = new SubType("Troy",24);



instance2.number.pop();



console.log(instance1.name + instance1.age + instance1.number); //Oliver1821,32,14,1

console.log(instance2.name + instance2.age + instance2.number); //Troy2421,32,14


三、组合继承（伪经典继承）


1、无参数




function SuperType(){

  this.color = ["red","yellow","white"];

}

SuperType.prototype.sayColor = function(){

  return this.color;

};



function SubType(){

  SuperType.call(this);

  this.number = 321;

}

SubType.prototype = new SuperType();

SubType.prototype.constructor = SubType;

SubType.prototype.sayNumber = function(){

  return this.number;

};



var instance1 = new SubType();

var instance2 = new SubType();



instance2.color.pop();

console.log(instance1.color + instance1.number); //red,yellow,white321

console.log(instance2.color + instance2.number); //red,yellow321


2、有参数




function SuperType(name){

  this.name = name;

  this.number = [32,1342,11,1];

}

SuperType.prototype.sayName = function(){

  return this.name;

};



function SubType(name,age){

  SuperType.call(this,name);

  this.age = age;

}

SubType.prototype = new SuperType();

SubType.prototype.constructor = SubType;

SubType.prototype.sayAge = function(){

  return this.age;

};



var instance1 = new SubType("Oliver",18);

var instance2 = new SubType("Troy",24);



instance2.number.pop();

console.log(instance1.sayName() + instance1.sayAge() + instance1.number); //Oliver1832,1342,11,1

console.log(instance2.sayName() + instance2.sayAge() + instance2.number); //Troy2432,1342,11


三、寄生组合式继承（引用类型最理想的范式）




function inheritPrototype(subType,superType){

  var prototype = Object(superType.prototype);

  prototype.constructor = subType;

  subType.prototype = prototype;

}



function SuperType(name){

  this.name = name;

  this.number = [321,321,43];

}

SuperType.prototype.sayName = function(){

  return this.name;

};



function SubType(name,age){

  SuperType.call(this,name);

  this.age = age;

}

inheritPrototype(SubType,SuperType);

SubType.prototype.sayAge = function(){

  return this.age;

};



var instance1 = new SubType("Oliver",18);

var instance2 = new SubType("Troy",24);

instance2.number.pop();



console.log(instance1.sayName() + instance1.sayAge() + instance1.number); //Oliver18321,321,43

console.log(instance2.sayName() + instance2.sayAge() + instance2.number); //Troy24321,321


或者可以把inheritPrototype 函数写成下面这样：




function inheritPrototype(SubType,SuperType){

  SubType.prototype = new SuperType();

  SubType.prototype.constructor = SubType;

}


四、原型式继承（用于共享引用类型的值，与寄生式类似）


1、传统版（先定义object() 函数，再继承）




function object(o){

  function F(){};

  F.prototype = o;

  return new F();

}



var SuperType = {

  name: "Oliver",

  number: [321,321,4532,1]

};



var SubType1 = object(SuperType);

var SubType2 = object(SuperType);



SubType1.name = "Troy";

SubType1.number.pop();



SubType2.name = "Alice";

SubType2.number.pop();



console.log(SubType1.name + SubType2.name + SubType1.number + SubType2.number + SuperType.name + SuperType.number); //TroyAlice321,321321,321Oliver321,321


ECMAScript 5 版（直接用Object.create()，再继承）




var SuperType = {

  name: "Oliver",

  number: [321,321,4532,1]

};



var SubType1 = Object.create(SuperType); //省略了定义object()函数

var SubType2 = Object.create(SuperType);



SubType1.name = "Troy";

SubType1.number.pop();



SubType2.name = "Alice";

SubType2.number.pop();



console.log(SubType1.name + SubType2.name + SubType1.number + SubType2.number + SuperType.name + SuperType.number); //TroyAlice321,321321,321Oliver321,321


ECMAScript 5 简写版（定义Object.create()的第二个参数，再继承）




var SuperType = {

  name: "Oliver",

  number: [321,321,4532,1]

};



var SubType1 = Object.create(SuperType,{

  name: {

    value : "Troy"

  }

});

var SubType2 = Object.create(SuperType,{

  name: {

    value : "Alice"

  }

});



SubType1.number.pop();

SubType2.number.pop();



console.log(SubType1.name + SubType2.name + SubType1.number + SubType2.number + SuperType.name + SuperType.number); //TroyAlice321,321321,321Oliver321,321


寄生式继承（用于共享引用类型的值，与原型式类似）




function createAnother(original){

  var clone = Object(original);

  clone.sayHi = function(){

    return "Hi";

  };

  return clone;

}



var person = {

  name: "Oliver",

  number: [13,21,31,1]

};



var anotherPerson = createAnother(person);

anotherPerson.number.pop();



console.log(anotherPerson.sayHi() + anotherPerson.number); //Hi13,21,31

console.log(person.number); //13,21,31


以上就是本文的全部内容，希望对大家的学习有所帮助。




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