The This keyword in JavaScript points to a problem

1. Purely function calls, this represents global objects

var x = 1; function Test () {    var x = ' er ha ';    Console.log (this. x);    // 1 }test ();

2, as a member method of an object, this represents the object

x = ' er ha ' ;
function  Test () {    console.log (this. x);      //1}  var obj = {    1,    Fn:test}obj.fn ();

3, as a constructor call, this represents the new object that is generated by the ' new ' keyword

x = ' er ha ' ;
function  Test () {
this. x = 1;} var New test (); Console.log (obj.x)     // 1

4. When using the call () method or Apply (), the first parameter of this method is the object that called the function after the change, this refers to the first parameter, when the argument is empty, the global object is called by default

var x = 1; function Test () {Console.log (this. x);} var obj = {    ' er ha ',    fn:test};obj.fn.apply ();     // 1       

The This keyword in JavaScript points to a problem