easy to use deferred shim

_deferred_shim.js

//requires jQuery.Deferred

_deferred = (function(){
    var that = {};
    var deferred = {};
    var lazy = function(name) {
        if(!deferred[name]){
            deferred[name] = $.Deferred();
        }
        return deferred[name];
    };

    that.resolve = function(name, arg) {
        return lazy(name).resolve(arg);
    };
    that.resolveCallback = function(name, arg){ //version of 'resolve' that can be used as a callback
        return function(){
            that.resolve(name, arg);
        }
    };
    that.done = function(name, fn) {
        return $.when.apply($, _.map(_.isArray(name) ? name : [name], lazy)).done(fn);
    };

    return that;
}());

_deferred_shim_usage.js

//usage:
google.load('maps', '3', {other_params:'sensor=false', "callback" : _deferred.resolveCallback('gmap')}); 
(function(d){
    var js, id = 'facebook-jssdk', ref = d.getElementsByTagName('script')[0];
    if (d.getElementById(id)) {return;}
    js = d.createElement('script'); js.id = id; js.async = true;
    js.src = "//connect.facebook.net/en_US/all.js";
    ref.parentNode.insertBefore(js, ref);
}(document));

// Init the SDK upon load
window.fbAsyncInit = function() {
    FB.init({
        appId      : XXX      
    });
    _deferred.resolve('facebook');
};

//do some stuff after google maps load:
_deferred.done('gmap', function(){
   ... 
});

//do some stuff after google maps and facebook load:
_deferred.done(['gmap', 'facebook'], function(){
   ... 
});