Why would a JavaScript variable start with a dollar sign? [duplicate]

Answer 1

As I have experienced for the last 4 years, it will allow some one to easily identify whether the variable pointing a value/object or a jQuery wrapped DOM element

Ex:
var name = 'jQuery';
var lib = {name:'jQuery',version:1.6};

var $dataDiv = $('#myDataDiv');

in the above example when I see the variable "$dataDiv" i can easily say that this variable pointing to a jQuery wrapped DOM element (in this case it is div). and also I can call all the jQuery methods with out wrapping the object again like $dataDiv.append(), $dataDiv.html(), $dataDiv.find() instead of $($dataDiv).append().

Hope it may helped. so finally want to say that it will be a good practice to follow this but not mandatory.