The analysis of this

This is a keyword in JS, when the function is run, an object is automatically generated and can only be used inside the function. This value changes as the letter is used, but always points to the object that called the function .

1. Purely function calls

function box () {    console.info (this),//window    this. x = "box";} Box (); Console.info (x); Box

The above description simply calls the function, which in the function represents window. I'll be writing two little chestnuts:

var x=1; function box () {    console.info (this. x);  // 1 }box ();

var x=1; function box () {    this. x =2;} Box (); Console.info (x); // 2

2. As a method of an object

When a function is called as a method of an object, this represents the object

The next three chestnuts are the most common method.

function test () {   console.info (this.x);} var o = {};o.x = 1;O.M=TEST;O.M ();//1,this stands for O

　

var o = {};o.x = 1;o.m =function () {    console.info (this.x);} O.M ();//1,this representative O

　　

var o={    x:1,    m:function () {         console.info (this.x)       }}o.m ();//1 this represents O

　　

3. Call as a constructor

That is, a new object is generated by the constructor, this represents the new object, which is very common.

function box () {    this. x = 1;  }  var New box (); Console.info (box1.x);//1 This represents Box1 object

4.apply Call

Apply is the method used to change the object that invokes the function, the first parameter represents the changed object, and the remaining parameter represents the passed-in parameter

var x = 0;function box () {    console.info (this.x);} var o={    x:1,    m:box}o.m ();//1o.m.apply ();//0o.m.apply (o);//1

Notice that when apply is passed, the delegate passes the window.

The analysis of this