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1)原型链

  ①原型链示例

function Shape() {
    this.name = 'shape';
    this.toString = function(){
        return this.name;
    }
}

function TwoDshape () {
    this.name = '2D shape';
}

function Triangle (side,height) {
    this.name = 'Triangle';
    this.side = side;
    this.height = height;
    this.getArea = function () {
        return this.side * this.height / 2;
    }
}

TwoDshape.prototype = new Shape();
Triangle.prototype = new TwoDshape();   //用new新建对象实体,并赋值覆盖该对象的原型
TwoDshape.prototype.constructor = TwoDshape;
Triangle.prototype.constructor = Triangle; 

var my = new Triangle(5,10); 
my.getArea();       //25
console.log(my.toString());//继承的方法,具体步骤(遍历my对象属性没有找到,接着查看my.__proto__所指向的对象,即new TwoDshape()创建的实体,
//依然没找到,又继续查找该实体的__proto__所指向的对象,即new Shape()所创建的实体,找到toString方法,并在my对象中被调用,this指向my)


//通过instanceof操作符,我们可以验证my对象同时是上面三个构造器的实例
my instanceof Shape;          //true
my instanceof  TwoDShape;     //true
my instanceof Triangle;      //true

//我们也可以用其他两个构造器来创建对象,用new TwoDshape()所创建的对象也可以获得继承自Shape()的toString()方法
var td = new TwoDshape();
td.constructor === TwoDshape; //true;
td.toString();          // 2D shape

var s = new Shape();
s.constructor === shape;    // true;

 ②将共享属性迁移到原型中去

function Shape(){this.name='shape'}//使用new Shape()新建对象,每个实体都有全新的属性并占用独立空间
function Shape(){};Shape.prototype.name='shape';//属性移到原型后,使用new新建对象时,不再含自己独立的这个属性

2)只继承于原型

Triangle.prototype=Shape.prototype;//减少继承方法的查询步骤
Triangle.prototype.name='Triangle';//修改子对象原型后父对象原型也随即被改,即再new Shape()新建对象时,新对象name为‘Triangl

  ②临时构造器——new F()

function Shape() {}
Shape.prototype.name = "shape";
Shape.prototype.toString = function () {
    return this.name;
}


function TwoDshape() {}
var F = function () {};
F.prototype = Shape.prototype;
TwoDshape.prototype = new F();
TwoDshape.prototype.constructor = TwoDshape;
TwoDshape.prototype.name = '2D shape';


function Triangle(side, height) {
    this.side = side;
    this.height = height;
}
var F = function () {};
F.prototype = TwoDshape.prototype;
Triangle.prototype = new F();
Triangle.prototype.constructor = Triangle;
Triangle.prototype.name = 'Triangle';
Triangle.prototype.getArea = function () {
    return this.side * this.height / 2;
}


var my = new Triangle (5,10);
alert(my.getArea());

//通过这种方法,我们仍然能保持住原型链
my._proto_ === Triangle.prototype;             //true
my._proto_.constructor === Triangle;            //true
my._proto_._proto_ === TwoDshape.prototypr;        //true
my._proto_._proto_._proto_.constructor === Shape;_    //true

//并且父对象的属性不会被子对象覆盖:
var s = new Shape();
s.name; // shape

//calling toString()
"I am a" + new TwoDshape();     //I am a 2D shape   
                         

 3)uber—子对象访问父对象的方式

function Shape(){}
Shape.prototype.name='shape';
Shape.prototype.toString=function(){
  var const = this.constructor;
  return const.uber
     ? this.const.uber.toString() + ',' + this.name
     : this.name;
}
function TwoDShape(){} var F=function(){} F.prototype=Shape.prototype; TwoDShape.prototype=new F(); TwoDShape.prototype.constructor=TwoDShape; TwoDShape.uber=Shape.prototype; TwoDShape.prototype.name='2D shape'; function Triangle(side,height){ this.side=side; this.height=height; } var F=function(){} F.prototype=TwoDShape.prototype; Triangle.prototype=new F(); Triangle.prototype.constructor=Triangle; Triangle.uber=TwoDShape.prototype; Triangle.prototype.name='triangle'; Triangle.prototype.getArea=function(){return this.side*this.height/2}; var my=new Triangle(5,10) console.log(my.toString());//shape,2D shape,triangle

 4)将继承部分封装成函数

function extend (Child,Parent) {
    var F = function () {};
    F.prototype = Parent.prototype;
    Child.prototype = new F();
    Child.prototype.constructor = Child;
    Child.uber = Parent.prototype;
}


extend(TwoDsgape,Shape);
extend(Triangle,TwoDshape);

5)属性拷贝

/*属性拷贝执行的是对象原型的逐一拷贝,而非简单的原型链查询。
  所以需要特别注意的是:
    这种方法仅适用于包含基本数据类型的对象,
    所有的对象类型(包括函数和数组)都是不可复制的,
    因为他们只支持引用传递      
*/

function extend2(Child,Parent){
    var p = Parent.prototype;
    var c = Child.prototype;
    for(var i in p){
        c[i] = p[i];
    }
    c.uber = p ;
}

6)小心处理引用拷贝

var A=function(){},B=function(){};
A.prototype.stuff=[1,2,3];
A.prototype.name='a';
extend2(B,A);//让B继承A使用方法二
B.prototype.name+='b';//ab,A.prototype.name依然为a,因为拷贝的是值
B.prototype.stuff.push(4);//此时A和B原型上的stuff同时被修改,因为拷贝的是应用
B.prototype.stuff=['a','b','c']//如果完全重写事情就不一样了,A为原来,B为新的

7)对象之间的继承(不使用构造器)

function extendCopy (p) {
    var c = {};
    for (var i in p){
        c[i] = p[i];
    }
    c.uber = p;
    return c;
}

var shape ={
    name = 'shape',
    toString :function () {
        return this.name;
    }
}

var twoDee = extendCopy(shape);
twoDee.name = '2D shape';
twoDee.toString = function () {
    return this.uber.toString() + ',' + this.name;
}

//下面我们让triangle对象继承一个2D图形对象
var triangle = extendCopy(twoDee);
triangle.name = 'Triangle'
triangle.getArea = function () {
    return this.side * this.height / 2;
}


//使用triangle
triangle.side = 5;
triangle.height = 10;
triangle.getArea();          //25

triangle.toString();        // shape,2D shape,Triangle

8)深拷贝(当遇到对象类型时,再次调用拷贝)

function deepCopy(p,c){
    c = c || {};
    for (var i in p){
        if(p.hasOwnProperty(i)){
            if(typeof p[i] === 'object'){
                c[i] = Array.isArray(p[i]?[]:{});
                deepCopy(p[i],c[i]);
            }else{
                c[i] = p[i]
            }
        }
    }
    return c;
}

var parent = {
    numbers:[1,2,3],
    letters:['a','b','c'],
    obj:{
        prop : 1
    },
    bool : true
};

//我们分别用深拷贝和浅拷贝测试一下,就会发现两者的不同。
//在深拷贝中,对对象的numbers属性进行更新不会对原对象产生影响。

var mydeep = deepCopy(parent);
var myshallow = extendCopy(parent);

mydeep.numbers.push(4,5,6);
mydeep.numbers     //[1,2,3,4,5,6]
parent.numbers     //[1,2,3]

myshallow.numbers.push(10);
myshallow.numbers   //[1,2,3,10]
parent.numbers      //[1,2,3,10]

9)object()(用object函数来接受父对象,并返回一个以该对象为原型的新对象)

function object(o){
  var n;
  function F(){}
  F.prototype=o;
  n=new F();
  n.uber=o;
  return n;
}//这个函数与extendcopy基本相同

10)原型继承与属性拷贝的混合应用

function objectplus(o,stuff){
  var n;
  function F(){}
  F.prototype=o;
  n=new F();
  n.uber=o;
  for(var i in stuff){n[i]=stuff[i]}
  return n;
}//两对象o用于继承,stuff用于拷贝方法与属性

11)多重继承(一个对象中有不至一个父对象的继承)

function multi(){
  var n={},stuff,j=0,len=arguments.length;
  for(j=0;i<len;j++){
    stuff=arguments[j];
    for(var i in stuff){n[i]=stuff[i]}
  }
  return n;
}//内层循环用于拷贝属性,外层循环用于遍历多个父对象参数,若有相同属性后面替代之前

12) 寄生式继承

13)构造器借用

待续...