javaScript面向对象编程-继承（二）

原型继承

原型继承是对类式继承的一种封装，其中的过渡对象就相当于类式继承中的子类，只是在原型式中作为一个过渡对象出现，目的是创建要返回的新的实例化对象。和类式继承一样，父类对象book中指类型的属性被复制，引用类型的属性被共有。

//原型是继承
function inheritObject(o) {
//声明一个过渡函数对象
function F(){}
//过渡对象的原型继承父类
F.prototype = o;
//返回过渡对象的一个实例，该实例的原型继承了父对象
return new F();
}

var book ={
name:"js",
alikeBook:["css","html"]
};
//测试代码
var newBook = inheritObject(book);
newBook.name ="ajax";
newBook.alikeBook.push("new xml book");
var otherBook = inheritObject(book);
otherBook.name ="flash";
otherBook.alikeBook.push("other as book");
console.log(newBook.name);//ajax
console.log(newBook.alikeBook);//[ 'css', 'html', 'new xml book', 'other as book' ]
console.log(otherBook.name);//flash
console.log(otherBook.alikeBook);//[ 'css', 'html', 'new xml book', 'other as book' ]
console.log(book.name);//js
console.log(book.alikeBook);//[ 'css', 'html', 'new xml book', 'other as book' ]

寄生式继承

寄生式继承是对原型继承的第二次封装，并且在封装的过程中对继承对象进行了扩展，这样新创建的对象不仅仅有父类中的属性和方法，而且添加了新的属性和方法。

//寄生式继承var newBook = createBook(book);newBook.name = "js";newBook.alikeBook.push("new");var otherBook = createBook(book);otherBook.name = "bad";otherBook.alikeBook.push("other");
//声明基对象
var book = {
name:'js book',
alikeBook: ["css","html"]
};
function createBook(obj) {
//通过原型继承方式创建新对象
var o = new inheritObject(obj);
o.getName = function () {
console.log(name);
}
//返回拓展后的新对象
return o;
}
//测试代码
var newBook = createBook(book);
newBook.name = "js";
newBook.alikeBook.push("new");
var otherBook = createBook(book);
otherBook.name = "bad";
otherBook.alikeBook.push("other");
console.log(newBook.name);//ajax
console.log(newBook.alikeBook);//[ 'css', 'html', 'new xml book', 'other as book' ]
console.log(otherBook.name);//flash
console.log(otherBook.alikeBook);//[ 'css', 'html', 'new xml book', 'other as book' ]
console.log(book.name);//js
console.log(book.alikeBook);//[ 'css', 'html', 'new xml book', 'other as book' ]