In Javascript/JQuery what is $. for?

Question

I'm writing a utility file and I've gotten some examples from online and this a form of writing the utility I've come across:

$.util = $.extend($.util || {}, {

    //functions here...

});

and so I think I understand what it's doing. It allows me to call $.util.function() somewhere else, however when I remove the . in front of the $ the code breaks. What does this notation mean? What's the difference between $. and $?

http://stackoverflow.com/questions/1049112/what-is-the-meaning-of-symbol-in-jquery — Jean-Claude Colette, Oct 02 '16 at 09:57
If you think of `$` as a synonym for `jQuery` then it becomes clear why "jQueryutil" doesn't work. — JJJ, Oct 02 '16 at 09:58

Sergio Tulentsev · Accepted Answer · 2016-10-02T10:00:06.053

6

$.util = something means "assign something to property util of object $".

$util = something means "assign something to variable $util"

Similarly, $.extend is "get value of property extend of object $" (which is a function in this exact scenario) and $extend is "get value of variable $extend"

edited Oct 02 '16 at 10:00

answered Oct 02 '16 at 09:55

Sergio Tulentsev

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ohh shoot. I thought that adding `$` onto any variable would automatically make it jQuery. I'm not sure why I thought that but that makes sense. Thank you! – Van-Sama Oct 02 '16 at 09:58

score 4 · Answer 2 · answered Oct 02 '16 at 09:57

If you're using jQuery, $ is just a variable contaning the jQuery object. So by writing $., you're essentially accessing jQuery properties and functions. Instead of $, you could also write jQuery and it should work the same way.

There's no special meaning to the $ character in JavaScript other than that. It acts like any other character, so $util is just a variable name.

score 3 · Answer 3 · answered Oct 02 '16 at 09:56

jQuery is an object that is assigned to both jQuery and $ on the window

It has methods that act on collections of elements eg $('.some-element').someMethod() and static methods that are just attached to the jQuery object but don't modify a collection, They are just normal function attached to the jQuery object to prevent exposing too many functions to the global context.

score 2 · Answer 4 · answered Oct 02 '16 at 09:59

$. - allows you to proceed to $ (jQuery) object property or method directly
$ - usually used as shortcut for invoking jQuery object

Whilst prefixing anything with $ won't make it jQueryable bec. this character can be used in variable name along with others (e.g. what is not applicable for PHP).

score 2 · Answer 5 · answered Oct 02 '16 at 10:07

Consider jQuery as a big class woth a lot of static functions and constructs.

The right way for calling any of its functions should be jQuery.someFunc() for static functions and var obj = jQuery('css selectors') for creating an object for HTML objects and then executing functions on that object.

Now for easier coding, jQuery added $ as an alias for jQuery. It's nothing more than an alias.

score 2 · Answer 6 · answered Oct 02 '16 at 10:08

Try this code:

  <script type="text/javascript">
    document.write('(jQuery === $) is ' + (jQuery === $) + '<br />');
    document.write('typeof(jQuery) = ' + typeof(jQuery) + '<br />');
  </script>

You will see:

(jQuery === $) is true

typeof(jQuery) = function

So jQuery is a function with a bunch of extra properties and functions attached to it.

If you're coming from a strongly-typed language background, the concept of attaching properties and methods to a function might seem strange, but you can do it in javascript.

In Javascript/JQuery what is $. for?

6 Answers6