Is there any specific reason behind using $ with variable in jQuery

Solution 1:

No there is no real difference.

It's just a convention that helps you remember that a isn't the DOM element but it's a jQuery object.

var a = document.getElementById('a');
a.innerHTML  //fine

var $a = $('#a');
$a.html()   // fine

Ohhh, and by the way, neither a or $a are good variable names ... you should use meaningful variable names not abc characters.

Read the jQuery info tag on this very same site:

Variable Naming Conventions

jQuery wrapped variables are usually named starting with '$' to distinguish them from standard JavaScript objects.

var $this = $(this);

Solution 2:

It's only for showing that it's a Jquery variable.

Declaring $a you're showing that your variable is for JQuery objects, it's just a notation. So the most readable thing will be to declare Jquery variable with $ notation

var $obj=$("#obj");

And DOM element without $ notation

var obj = document.getElementById("obj");

Solution 3:

There's no difference. It's just a coding convention to help identify that the variable represents a jquery wrapped object.