From time to time you may want to include in your program other JavaScript frameworks or libraries with your code. If those frameworks use the dollar sign as a variable, this will cause conflicts. But, because jQuery plays nice with others, it has a method for avoiding these conflicts. To do so, use the $.noConflict(); method after loading the libraries that may conflict. This has the effect of reverting the dollar sign to its previous value. After invoking .noConflict(), use jQuery instead of $ to refer to the jQuery core. The following code demonstrates an example:
<html>
<head>
<script src=”conflictingFramework.js”></script>
<script src=”jquery.js”></script>
<script>
jQuery.noConflict();
jQuery(“<p>I am a paragraph</p>”).appendTo(body);
// $ references conflictingFramework.js, not jQuery
$.blahMethodFromOtherLibrary();
</script>
</head>
<body>
</body>
</html>
Opening up the hood, you can see the actual definition of $.noConflict():
…
noConflict: function( deep ) {
window.$ = _$;
if ( deep ) {
window.jQuery = _jQuery;
}
return jQuery;
},
…
As you can see, it’s very short. jQuery maintains an internal reference to the value of $ — after $.noConflict is called, the value of $ is restored to its previous value, which is the value of the conflicting library.
Source: Otero Cesar, Rob Larsen (2012), Professional jQuery, John Wiley & Sons, Inc