理解js对象继承的N种模式

2019-11-20 10:42:43

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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); //Oliver1821,32,14,1console.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,white321console.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); //Oliver1832,1342,11,1console.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); //Oliver18321,321,43console.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); //Hi13,21,31console.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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