理解js对象继承的N种模式

时间:2021-05-18

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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