Immediately-Invoked Function Expression (IIFE)

IIFE.js

 // IIFE 
 (function(){ /* code */ }()); // Crockford recommends this one
 (function(){ /* code */ })(); // But this one works just as well
 
 // if you use mootools and jQuery in compat mode and  mootools exposes $ and jQuery jQuery like so:
<script src="mootools.js"></script>
<script src="jquery.js"></script>
var jQuery = jQuery.noConflict();

 // then you can use legacy code which uses jQuery like so
 (function($){
    // $ === jQuery
    // your legacy code here
 })(jQuery);
 
  // and legacy code which uses mootools like so:
 (function($){
    // $ === mootools
    // your legacy code here
 })($);