call 和 apply 方法

1：每个函数都包含两个非继承而来的方法：call(),apply().

2：call方法和apply方法作用是一样的。

下边是call的使用例子：

 window.color = 'red';
 document.color = 'yellow';
 var s1 = {color: 'blue'};

 function getColor (){
     console.log(this.color);
 }
 getColor.call(); //red (默认传递参数)
 getColor.call(window);// red
 getColor.call(document);//yellow
 getColor.call(s1);//blue
 getColor.call(this);//red

 var Pet={
   words : '...',
   speak : function(say){console.log(say+ ' ' + this.words);}
 }

 Pet.speak('howling'); //howling...

 var Dog = {words: 'wang wang'}

 Pet.speak.call(Dog, 'barking');// barking wang wang

下边是apply使用例子

 window.number = 'one';
 document.number = 'two';
 var s2 = {number: 'three'};

 function getNum(){ console.log(this.number); }

 getNum.apply(); // one 默认
 getNum.apply(window); //one
 getNum.apply(document);//two
 getNum.apply(s2);//three
 getNum.apply(this);//one

 function Pet(words){
   this.words = words;
   this.speak = function(){ console.log(this.words) }
 }

 function Dog(words){
    // Pet.call(this, words);
    Pet.apply(this, arguments);
 }

 var dog = new Dog('wang wang');
 dog.speak();// wang wang

3：不同点是接收参数的方式不同。

function add(c,d){ return this.a + this.b + c + d;}

var s = {a:1, b:2};
console.log( add.call(s,3,4) );// 1+2+3+4 =10
console.log( add.apply(s,[3,4]) ); // 1+2+3+4 =10

 window.firstName = "tomF";
 window.lastName = "tomL";
 var myObj = {firstName:"myF", lastName:"myL"};

 function getName(){ console.log(this.firstName + this.lastName); }

 function getMess(sex, age){
     console.log(this.firstName + this.lastName+ "性别:"+sex+"age:"+age);
 }

 getName.call(window);//tomFtomL
 getName.call(myObj);//myFmyL
 getName.apply(window);//tomFtomL
 getName.apple(myObj);//myFmyL

 getMess.call(window,'girl',21);//tomFtomL性别：girlage：21
 getMess.apply(window,['girl',21]);//tomFtomL性别：girlage：21
 getMess.call(myObj,'unknown',30);//myFmyL性别：unknownage：30
 getMess.apply(myObj,['unknown',30]);//myFmyL性别：unknownage：30