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1. 原型链继承
子类使用基类对象重写prototype
function SuperType(){ this.property = true; } SuperType.prototype.getSuperValue = function(){ return this.property; }; function SubType(){ this.subproperty = false; } //inherit from SuperType SubType.prototype = new SuperType(); //new method SubType.prototype.getSubValue = function (){ return this.subproperty; }; //override existing method SubType.prototype.getSuperValue = function (){ return false; }; var instance = new SubType(); alert(instance.getSuperValue()); //false
主要缺点: 通过原型来继承时, 原型会变成另一个类型的实例, 所以, 原先实例属性被变成了子类中的原型属性.
2. 借用构造函数
子类中使用call/apply调用基类构造函数方法
function SuperType(name){ this.name = name; } function SubType(){ //inherit from SuperType passing in an argument SuperType.call(this, "Nicholas"); //instance property this.age = 29; } var instance = new SubType(); alert(instance.name); //"Nicholas"; alert(instance.age); //29
缺点: 并非真正的继承, 无法执行基类中原型的方法.
3. 组合继承(伪经典继承)
既执行借用构造函数, 又执行原型链传递, 是最常用的继承方式.
其最大问题是 无论什么情况下,都会调用两次超类型的构造函数.
function SuperType(name){ this.name = name; this.colors = ["red", "blue", "green"]; } SuperType.prototype.sayName = function(){ alert(this.name); }; function SubType(name, age){ SuperType.call(this, name); this.age = age; } SubType.prototype = new SuperType(); SubType.prototype.sayAge = function(){ alert(this.age); }; var instance1 = new SubType("Nicholas", 29); instance1.colors.push("black"); alert(instance1.colors); //"red,blue,green,black" instance1.sayName(); //"Nicholas"; instance1.sayAge(); //29
4. 原型式继承
思路是借用原型来基于已有的对象创建新对象.
function object(o){ function F(){} F.prototype = o; return new F(); } var person = { name: "Nicholas", friends: ["Shelby", "Court", "Van"] }; var anotherPerson = object(person); /* 注意, 在ES5中新增了Object.create()方法规范了原型式继承, 该方法接受两个参数, 一个是用作新对象原型的对象, 一个为新对象定义的额外方法 var anotherPerson = Object.create(person); */ anotherPerson.name = "Greg"; anotherPerson.friends.push("Rob"); var yetAnotherPerson = object(person); yetAnotherPerson.name = "Linda"; yetAnotherPerson.friends.push("Barbie"); alert(person.friends); //"Shelby,Court,Van,Rob,Barbie" 子类中对对象的修改会影响基类的对象的调用.
5. 寄生式组合式继承
主要用于解决组合继承中调用两次构造函数的问题, 该方法通过借用构造函数来继承属性, 通过原型链的混成形式来继承方法.
其高效率体现在它只调用了一次SuperType的构造函数, 避免了在SubType的prototype上创建不必要的, 多余的属性, 目前最理想的继承方式.
function object(o){ function F(){} F.prototype = o; return new F(); } function inheritPrototype(subType, superType){ var prototype = object(superType.prototype); //create object prototype.constructor = subType; //augment object subType.prototype = prototype; //assign object } function SuperType(name){ this.name = name; this.colors = ["red", "blue", "green"]; } SuperType.prototype.sayName = function(){ alert(this.name); }; function SubType(name, age){ SuperType.call(this, name); this.age = age; } inheritPrototype(SubType, SuperType); SubType.prototype.sayAge = function(){ alert(this.age); }; var instance1 = new SubType("Nicholas", 29); instance1.colors.push("black"); alert(instance1.colors); //"red,blue,green,black" instance1.sayName(); //"Nicholas"; instance1.sayAge(); //29
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原文地址：http://www.cnblogs.com/html5css3js/p/4507247.html
