The this in JS is so magical that I get dizzy.

A common judgment of this:

1. function pre-compilation process This -> Window

2. global scope in this -> Window

3.call/apply can change when the function runs this point

4.obj.func (); the This in func () points to obj(that is, who calls the function and this in the function points to whom)

Second, the common use of this:

1. In the custom constructor:

　　　

function A () {        this. Name = ' a ';          this. Age =;    }

2. In the function definition of the object, this point points to the object, which can be called within the function by this object's properties.

　　

var obj = {        ' lyl ',        function  () {            Console.log (this // lyl         }    }

3. Define the method on the prototype chain:

　　

function () {        //  This refers to an array that invokes the method    }

4. When JS defines an event:

　　

function () {        //  This points to the DOM object,  $Li this        . Style.color = ' red ';    }

Three, Strict mode:

ES5 in non-strict mode, this default points to window

ES5 Strict mode, this initial default is undefined, you need to assign a value, and why is the assignment, assignment is Undefined/null is no exception

The this in JS is so magical that I get dizzy.