When/why to prefix variables with “$” when using jQuery? [duplicate]

Possible Duplicate:
Why would a javascript variable start with a dollar sign?

I see people using the dollar sign in front of variables when using jQuery. Is there any reason behind this? I'm I missing something basic or is it just a common practice?



It's a common reference to a jQuery wrapped object. It makes reading the code easier to know which variables are jQuery wrapped.

//Item has been "cached" for later use in the script as a jQuery object.
var $item = $(this);

For me a common practice is this:

If a variable is private I use an underscore like this:

     var _foo = "bar";

If it's public I'll use no underscore:

var foo = "bar"

And if it's a jQuery selector I'll use the $:

var $foo = $('bar');
//then you can access it like this

It's just coding convention and it allows you to quickly reference what type the variable is later in the code.


Many people using jQuery will prefix variables that contain a jQuery object with a $, so that they are easily identified. Consider this example:

var $img = $(".someclass span.otherclass img");
/* somewhere later in the code */
$img.bind("click", function() {/*...*/});

In my experience this is just a readability. Some developers like to prefix their variables so that they are easy to spot. It could also be a PHP habit creeping it's way in to Javascript.


Dollar signs in code that uses JQuery commonly means that the variable in question is a jQuery variable (an object wrapped by jquery).


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