JS In this usage example detailed

1. Point to Window

Global variables

1	Alert (this)//Back [object Window]

Global functions

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function SayHello () {alert (this);} sayhello ();

2. Point to the object (in the global inside this point to window, within an object this point to the object, within the closure this point to window)

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var user= "the window"; var box={User: ' The box ', Getthis:function () {return this.user}, Getthis2:function () {return function () {return this.us Er } } }; alert (this.user);//the Window alert (Box.getthis ());//the box alert (Box.getthis2 ()); The window (because the closure is used, here's this point to Window) alert (Box.getthis2 (). Call (box)); The box object is impersonating (this here is pointing to the box object)

3. Change the this point of the function with Apply,call

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function sum (NUM1, num2) {return num1+num2} function box (NUM1, num2) {return sum.apply (this, [Num1, num2]);//this represents win Dow scope Box pretends sum to execute} console.log (Box (10,10)); 20

4. New Object

func tion person () {Console.log (this)//point this to a new empty object} var p = new person ();