main.js

// IIFE - Immediately Invoked Function Expression
  (function($, window, document) {

    // The $ is now locally scoped 

   // Listen for the jQuery ready event on the document
   $(function() {

     // The DOM is ready!

   });

   // The rest of the code goes here!

  }(window.jQuery, window, document));
  // The global jQuery object is passed as a parameter