This keyword usage in Javascript

In JavascriptthisAlways refers to the "owner" of the function we're re executing, or
Rather, to the object that a function is a method.

function doSomething() {   this.style.color = '#cc0000';}

------------ window --------------------------------------|                                          / \           ||                                           |            ||                                          this          ||   ----------------                        |            ||   | HTML element | <-- this         -----------------  ||   ----------------      |           | doSomething() |  ||               |         |           -----------------  ||          --------------------                          ||          | onclick property |                          ||          --------------------                          ||                                                        |----------------------------------------------------------

1. Copy---------------Traditional event registration--------------the element

element.onclick = doSomething;

The function is copied in its entirety toonclickProperty (which now becomes a method). So if the event handler is executedthisRefers
To the HTML Element and ItscolorIs changed.

------------ window --------------------------------------|                                                        ||                                                        ||                                                        ||   ----------------                                     ||   | HTML element | <-- this         -----------------  ||   ----------------      |           | doSomething() |  ||               |         |           -----------------  ||          -----------------------          |            ||          |copy of doSomething()|  <-- copy function    ||          -----------------------                       ||                                                        |----------------------------------------------------------

Examples of elements:

element.onclick = doSomethingelement.addEventListener('click',doSomething,false)element.onclick = function () {this.style.color = '#cc0000';}<element onclick="this.style.color = '#cc0000';">

2. Reference ------------- inline
Event registration ------------ this points to the global variable window

doSomething();

So it says "Go to dosomething () and execute it." When we arrivedoSomething()ThethisKeyword once again refers
To the global window object and the function returns error messages.

This indicates an example of a window object.

element.onclick = function () {doSomething()}element.attachEvent('onclick',doSomething)<element onclick="doSomething()">

From: http://www.quirksmode.org/js/this.html