librarySystemwithdependencies.js

(function() {
    var libraryStorage = {};

    function loadLibrary(libraryName, dependencyNames, addLibrary) {
        var dependencyValues = [];
        if (dependencyNames.length !== 0) {
            dependencyValues = dependencyNames.map(function(dependencyName) {
                return libraryStorage[dependencyName];
            })
        }
        libraryStorage[libraryName] = addLibrary.apply(null, dependencyValues);
    }

    function requireLibrary(libraryName) {
        return libraryStorage[libraryName];
    }

    function librarySystem(libraryName, dependencyNames, addLibrary) {
        if (arguments.length > 1) {
            loadLibrary(libraryName, dependencyNames, addLibrary);
        } else {
            return requireLibrary(libraryName);
        }
    }

    window.librarySystem = librarySystem;
})();

// test
librarySystem('dependency', [], function() {
  return 'loaded dependency';
});

librarySystem('app', ['dependency'], function(dependency) {
  return 'app with ' + dependency;
});

librarySystem('app'); // 'app with loaded dependency'