Module loader interview question

loader.js

const _moduleRegistry = {};

// Adds a module to _moduleRegistry
function _addModule(name, deps) {
    const module = { name, deps };
    module.load = () => {
        console.log(`'${name}' loaded`);
        return module;
    }
    _moduleRegistry[name] = module;
}

// Returns promise when module is loaded from network
function _fetchModule(name) {
    const module = _moduleRegistry[name];
    return new Promise((resolve, reject) => {
        if (module) {
            setTimeout(() => resolve(module), Math.random() * 1000);
        }
        else {
            reject(new Error(`Module ${name} not found`));
        }
    })
}

(function _addModules() {
    _addModule('app', ['components', 'uilib']);
    _addModule('components', ['views', 'services']);
    _addModule('uilib', ['react', 'router']);
    _addModule('react', []);
    _addModule('router', ['react']);
    _addModule('models', []);
    _addModule('views', ['controllers', 'models']);
    _addModule('controllers', ['models']);
    _addModule('services', []);
    _addModule('tests', ['controllers', 'services']);
    console.log(_moduleRegistry);
})();


/******************************************************************************************/

/**
 * @param {string} entryModule - Entry module that needs to be loaded
 * Every module needs to load its dependencies before module.load() can be called.
 * Your task is to complete this method.
 * You can assume no cyclic dependencies and every dependency is available
 */
function loadModule(entryModule) {
    return _fetchModule(entryModule)
    .then(module => module.load())
}

// Load entry module
loadModule(`app`)
.then(module => console.log(`'${module.name}' and all its dependencies are loaded!`));