/*

* object.prototype.call

* @ 当一个object没有某个方法，但是其他的有，我们可以借助call或apply用其它对象的方法来操作。

* @ 语法: fun.call(thisArg[, arg1[, arg2[, ...]]])

* @ param: thisArg {object}     //当前引用对象

*   @ 不传参数,传null,undefined, this指向window对象

*   @ 传递另一个函数的函数名fun2, this指向函数fun2的引用

*   @ 传递一个对象,函数中的this指向这个对象

*   @ 值为原始值(数字,字符串,布尔值), this会指向该原始值的自动包装对象,如String,Number,Boolean

* @ param: arg1, arg2, ... {object}       // arguments参数

*/

function a(){

    console.log(this);

}

function b(){}

var objthis = {name: "Alan"};           //定义对象

a.call();               // window

a.call(null);           // window

a.call(undefined);      // window

a.call(1);              // Number {[[PrimitiveValue]]: 1}

a.call("");             // String {length: 0, [[PrimitiveValue]]: ""}

a.call(true);           // Boolean {[[PrimitiveValue]]: true}

a.call(b);              // function b(){}

a.call(objthis);        // Object {name: "Alan"}

function Product(name, price){

    this.name = name;

    this.price = price;

    if(price < 0){

        throw RangeError('Cannot create product ' + this.name + ' with a negative price');

    }

}

// call方法

function Food(name,price){

    Product.call(this,name,price);

    this.category = "food";

}

// 等同于

function Food(name,price){

    this.name = name;

    this.price = price;

    if(price < 0){

        throw RangeError('Cannot create product ' + this.name + ' with a negative price');

    }

    this.category = "food";

}

var animals = [

    {

        species: "Lion",

        name: "king"

    },

    {

        species: "Whale",

        name: "Fail"

    }

]

for(var i = 0; i < animals.length; i++){

    (function(i){

        this.print = function(){

            console.log("#" + i + " " + this.species + ": " + this.name);

        }

        this.print();

    }).call(animals[i],i);

    // 等同于

    /*(function(){

        this.print = function(){

            console.log("#" + i + " " + animals[i].species + ": " + animals[i].name);

        }

        this.print();

    })();*/

}

function greet(){

    var reply = [this.person, "Is An Awesome", this.role].join(" ");

    console.log(reply);

}

var obj = {

    person: "Douglas Crockford", role: "Javascript Developer"

};

greet.call(obj);

function changeStyle(attr, value){

     this.style[attr] = value;

}

var box = document.getElementById('box');

window.changeStyle.call(box, "height", "200px");

window.changeStyle.apply(box, ['height', '200px']);

function say(name){

        console.log(this + "," + name);

    }

    say.call2 = function( thisObj, arg1 ) {

        thisObj = new Object( thisObj );

        thisObj.say = this;

        return thisObj.say(arg1);

    };

    say.call2("hola","Mike");