custom.js

/**
Custom module for you to write your own javascript functions
**/
var Custom = function () {

    // private functions & variables

    var myFunc = function(text) {
        alert(text);
    }

    // public functions
    return {

        //main function
        init: function () {
            //initialize here something.            
        },

        //some helper function
        doSomeStuff: function () {
            myFunc();
        }

    };

}();

jQuery(document).ready(function() {    
   Custom.init(); 
});

/***
Usage
***/
//Custom.doSomeStuff();