AMD using ES6 module loaders

gistfile1.js

/*
// The default system module loader exposed by ES6 on the 
// global object.
Object.system = {
    load: function(name, callback, errback) {
        // ...
    },
    loaded: {}
}
*/


function define(name, requirements, callback, errback) {
    require(
        requirements, 
        function(mods) {
            var newMod = callback(mods);
            // Store the new module into the collection
            // of loaded modules for the current loader
            Object.system.loaded[name] = newMod;
        }, 
        function(errs) {
            errback(errs);
        }
    );
} 

function require(requirements, callback, errback) {
    var mios = {};
    var errs = {};
    var doneCount = 0;
    function checkDone() {
        if(doneCount == requirements.length) {
            if(Object.keys(errs).length > 0) {
                errback(new Error(errs));
            }else {
                var args = requirements.map(function(req) { return mios[req]; });
                callback.apply(undefined, args);
            }
        }
    }
    function incrDone() { doneCount++; checkDone(); }
    checkDone();
    requirements.forEach(function(req) {
        // Use the current loader to load the requested
        // modules.
        Object.system.load(
            req, 
            function(mio) { mios[req] = mio; incrDone() }, 
            function(err) { errs[req] = err; incrDone() }
        );
    });
}