Understand and skillfully use the call and apply in JS

Both call and apply are intended to change the context in which a function is run, in other words, to change the direction of this within the function body.

Because JavaScript functions have a concept of "context at definition" and "runtime context" and "context can be changed."

In JavaScript oop, we often define this:

function Cat () {
}
cat.prototype={
Food: "Fish",
Say:function () {
Alert ("I Love" +this.food);
}
}


var blackcat = new Cat;
Blackcat.say ();

But if we have an object Whitedog = {food: "Bone"}, we do not want to redefine it say method, then we can use call or Apply with Blackcat say method: BlackCat.say.call (Whitedog );

So, you can see that call and apply are meant to change this dynamically, and when an object does not have a method, but the others, we can use call or apply to manipulate other objects.

The DOM node chosen by document.getElementsByTagName is a type of array that is similar to array. It cannot apply methods such as Push,pop under the array. We can do this by:
var domnodes = Array.prototype.slice.call (document.getElementsByTagName ("*"));
This allows the domnodes to apply all the methods under the array. There's also the use of bind

Unlike call and apply, bind is not executed immediately after binding.

Add. bind (Sub, 5, 3);//no Return 8
Add. Bind (Sub, 5, 3) ();//8

Reference Link: http://www.cnblogs.com/52fhy/p/5118877.html

Understand and skillfully use the call and apply in JS