$ versus jQuery

We're switching from MooTools to jQuery at work. I have a coworker that told me never to use $ as the prefix when using a jQuery method (if I understood him correctly). He said that instead, the more appropriate or safer way (I didn't really follow him) was to use jQuery..

So instead of $.plugin(), jQuery.plugin() should be used, for example.

Why would that be the case? What distinction is he making with $/jQuery? Should I forget about the dollar sign as my accessor? Only in certain circumstances?

Why would that be the case? Is his $/jQuery distinction correct?

Because almost every JavaScript library defines a function called $. When you have many libraries in one document, conflicts may appear. If you are sure that jQuery is and always will be the only script defining that function, I wouldn't have anything against using $.

jQuery defines a nice solution to resolve conflicts: jQuery.noConflict. By using this function you can define your own name, whereby jQuery will be accessible, e.g.

var $jq = jQuery.noConflict(true);

Calling this function will result in restoring previous values for $ and jQuery variables when existed before initializing jQuery. I don't remember if any other libraries try to resolve name conflicts.

If you want to use $ instead of jQuery all the time you can run your code in a separate, private scope that holds the definition of $ by using a self-invoking function.

(function($){
   // your code goes here
   $("body").append("<p>Hello World!</p>");
})(jQuery); // or even jQuery.noConflict()

$ is aliased to jquery and could, in theory, be aliased to something else in another included library or script which may lead to confusion or worse. If you're only using jquery, using $ should be fine.

It's to avoid conflict with other libraries like Prototype that uses the same $.

I prefer the $, and there is no problem using it if you are using only Jquery.

In addition to the other answers around conflicts with other libraries, a variable name should always describe the variable. jQuery is a much more descriptive name for a variable than $.