Question

I’ve seen a few examples of this lately, and am rather curious why it happens.
( For example in the extjs source code, its all over the place )

var me=this;

or

var that=this;

And instead of referring to this, me is used.

Answer 1

This is usually done in case of a closure which need to access “this” when the closure was created.

For ex:

var obj = 
{
   name: "Hello",
   init : function() {
      var me = this;
      $("#txt").click ( function() {
         alert(me.name);
      });
   }
}

In the above example the init function in obj attaches an event handler to some txt element click event. This event handler needs to access the name property of obj object. Now inside the event handler the “this” will point to some other object (element on which event happens) and not to obj object. Hence we create a variable called me this points to this (obj) and this me is used inside the event handler to refer to obj.