LibrarySystem with Dependencies

library-system.js

(function() {
  var libraryStorage = {};
  
  var Library = function(dependencies, callback) {
    this.dependencies = dependencies;
    this.generator = callback;
  };

  function retreiveLibrary(libraryName) {
    var library = libraryStorage[libraryName];
    var dependencies;

    if(library.dependencies.length === 0) {
      return library.generator();
    } else {
      dependencies = library.dependencies.reduce(function(loadedDependencies, dependency) {
        loadedDependencies.push(retreiveLibrary(dependency));
        return loadedDependencies;
      }, []);

      return library.generator.apply(null, dependencies);
    }
  }

  function librarySystem(libraryName, dependencies, callback) {
    if(arguments.length > 2) {
      libraryStorage[libraryName] = new Library(dependencies, callback);
    } else {
      return retreiveLibrary(libraryName);
    }
  }
  
  window.librarySystem = librarySystem;
})();