Do you understand the object in Javascript that this is pointing to?

This is always confusing in Javascript, can you tell the output of the following three kinds of test1 (), Test2 (), Test3 ()?

Note: The following JavaScript is in the running environment for the browser

1 This is used in global functions

var x = 1;

function Test1 () {

var x = 5;

alert (this.x);

}

function _test2 () {

This.x = 5;

alert (this.x);

}

2 This is used in the constructor in new

function Test2 () {

var f = new _test2 ();

}

3 This is used in methods of the object

function _test3 () {

Alert (this.x)

}

function Test3 () {

var a = {};

a.x = 100;

A.show = _test3;

A.show ();

}

Figuring out the key to this point is:

function is used in different situations, this the value will change. But there is a general principle, that is , this refers to the object that called the function.

1. Test1 Call Scenario: equivalent to Window.test1 (), alert shows the value of the calling function X, which is window.x
2. Test2 the called scene: when the new keyword is generated, the object that this point refers to is the newly generated object _test2 ().
3. TEST3 Invocation Scenario: The function acts as a method call to an object, and this refers to the ancestor object, which is a

Do you understand the object in Javascript that this is pointing to?