How to use the functions of apply and call

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Although  apply and  call  can implement same function. However, there is a litter different between them. Please pay attention to look at the examples below:

 

Define an object Person

 

1 Person=function(name,age){2    this.name=name;3    this.age=age;7 }8 9 var pin=new Person("Pin",26); //create an object

 

After that, we need to define some functions (skating,running,eating) with different parameters respectively.

 1 function skating() // It don‘t need any parameter 2 { 3    alert(this.name+" like skating!"); 4 } 5  6 function running(distance) // It need 1 parameter 7 { 8    alert(this.name+" can only run "+distance+" meters!"); 9 }10 11 function eating(fruit1,fruit2) // It need 2 paramters12 {13    alert(this.name+" like eating "+fruit1+" and "+fruit2+"!");14 }

 

Now, I‘ll use apply and call respectively.

//after using applyskating.apply(pin); running.apply(pin,[1000]);eating.apply(pin,["apple","orange"]);Results respectively:Pin like skating!Pin can only run 1000 meters!Pin like eating apply and orange!

 

//after using callskating.call(pin); running.call(pin,1000);eating.call(pin,"apple","orange");Results respectively:Pin like skating!Pin can only run 1000 meters!Pin like eating apply and orange!

From the results above, we can know the differences between apply and call :

Same:

1. apply and call all can make object pin implement sakting, running and eating, respectively. Exactly, object pin own three new functions (sakting, running and eating).

2. The first parameter pin is the replace the key this among three functions. So, when the three functions call the variable this.name, the key this is NOT three functions themselves but object pin.

3. If the first paramter is null, the global object window will replace it.

4. If the function (such as skating) don‘t need any paramters, the apply and call are same.

 

Difference:

If the function need a parameter at least, the parameter should be a array using apply. For the call, without any constraints.