Defer loading js files companion script. Upon successfully parsed js files, re-run any function that has been attached to jquery ready function.

deferLoading.js

/**
 * Was based on code: https://gist.github.com/miguel-perez/476046a42d229251fec3
 * 
 * Replace jQuery's $.fn.ready() function with a mod exec
 * 
 * Sites that make heavy use of the $(document).ready function
 * are generally incompatible with asynchronous content. 
 * 
 * 
 * This script replaces the ready function with a 
 * module execution controller that 
 * 1. register function sent to __$.fn.ready__ 
 * 2. keep track of the js files that will be loaded async
 * and execute all of the functions when all the js files
 * have been downloaded.
 *
 * This avoid any dependency that might have between those files.
 * 
 * @author  Jourdein
 * @note    Should be placed directly after jQuery on the page
 * @date    2 November 2015
 */

(function($){
    var  $doc = $(document);

    /** create mod exec controller */
    $.readyFn = {
        libs: [],
        list: [],
        register: function(fn) {
            $.readyFn.list.push(fn);
        },
        isHandlerRegistered: function( handler ) {
            var isRegister = false;
            $.each($.readyFn.list, function(k, v) {
                if (v === handler) {
                    isRegister = true;
                    return false;
                }
            });
            return isRegister;
        },
        registerLib: function( lib ) {
            lib.onload = function() {
                libEl = this;

                // console.log('onloaded', this.src.substring(0, this.src.lastIndexOf('-')))

                $.readyFn.libs = $.readyFn.libs.filter( function (e) {
                    return e != libEl;
                });

                data = jQuery.hasData($(document)[0]) && jQuery._data($(document)[0])
                if (data) {
                    if (data.events['ready']) {
                        if (!$.readyFn.isHandlerRegistered( data.events['ready'][0].handler )) {
                            $.readyFn.register(data.events['ready'][0].handler)
                        }
                    }
                }

                if ( $.readyFn.libs.length == 0 ) {
                    $.readyFn.execute();
                    /*
                    Triggering 'load' event is wrapped in setTimeout.
                    I think, this to make sure the function/library succesfully initialize.
                    Some initialization involve binding to 'load' event. If the library wasn't yet bounded to the event, 
                    the trigger won't do anything.
                     */
                    setTimeout(function() {
                        //console.log('onLoad(readyState): %c %s %c %s ', 'background: #222; color: #bada55', document.readyState, 'background: #6fc; color: #4c4c4c', "☞ triggering window.load() ")
                        $(window).trigger('load')
                    },1000)
                }
            }
            $.readyFn.libs.push( lib );
        },
        execute: function() {
            for (var i = 0; i < $.readyFn.list.length; i++) { 
                //console.log(i)                   
                try {
                    //console.log( '('+$.readyFn.list.length+'/'+i+')executing ', $.readyFn.list[i])
                    $.readyFn.list[i].apply(document, [$])
                }
                catch (e) {
                    throw e;
                }
            };
        }
    };

    /** run all functions */
    $doc.ready(function(){
        $.readyFn.execute();
    });

    /** register function */
    $.fn.ready = function( fn ) {
        $.readyFn.register(fn);

        // preserve default behaviour
        // $.ready.promise().done( fn );
    };

})(jQuery);