What is use of self in jquery/ javascript?

Question

In javascript they are using like:

• var self=this;
• var jquery_element= $(html_element);
• self.jquery_element=jquery_elemnet

Why do we use these in javascript. I got this code from OpenStack horizon

Answer 1

var self=this; is useful for when you have nested functions and this can become ambiguous (in case you dont know this is a javascript keyword). self can be used to still change the this that now reffers to the this from the inner function.

var jquery_element= $(html_element); just provides a easy way to reference the jQuery element without having to constantly recreate it (also provides performance benefit for instance explained here).

self.jquery_element = jquery_element appears to be specific to that code and I'm not quite sure what it does.

Answer 2

It is for visibility in other scope, for using this from one scope, within other scope. Edit.

 var parentFunction = function(){
       this.msg = "hello world";
       var parentScopeSelf = this;
       var innerFunction = function(){
            var innerFunctionScopeSelf = this;
            console.log(this.msg);// undefined (because this now is   innerFunction scope, and does not have property msg)
            console.log(innerFunctionScopeSelf.msg);// undefined (because innerFunctionScopeSelf is "this" from  innerFunction scope, and does not have property msg)
            console.log(parentScopeSelf.msg);// hello world (because parentScopeSelf is "this" from parentFunction scope)
       }
    }