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