Understand and skillfully use the call and apply in JS

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 don't want to redefine it say method,

Then we can use The blackcat say method by call or apply :

BlackCat.say.call (Whitedog);//The popup prompt will be executed immediately

So, you can see that call and apply are in order to dynamically change this and appear when an object There is no method, but others, we can use call or apply The method of other objects to operate.

The Dom node selected by document.getelementsbytagname is an array -like 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.

Others do not mention, more and more confused.

Understand and skillfully use the call and apply in JS