(function() {
	var libraryStorage = {};

  // librarySystem now takes three arguments, including dependencyNames
	function librarySystem(libraryName, dependencyNames, callback) {
		if (arguments.length > 1) { // Create case
			var dependencies = [];
      // For each dependency name, use librarySystem to return the
      // corresponding library and push it to the dependencies array.
			dependencyNames.forEach(function(name) {
				dependencies.push(librarySystem(name));
			});
			// Unpack dependencies into callback arguments using spread (...) syntax
			libraryStorage[libraryName] = callback(...dependencies);
		} else { // Use case
			return libraryStorage[libraryName];
		}
	}

	window.librarySystem = librarySystem;

})();

// Usage:
// 1. Create our libraries:
librarySystem('name', [], function() {
  return 'Gordon';
});

librarySystem('company', [], function() {
  return 'Watch and Code';
});

librarySystem('workBlurb', ['name', 'company'], function(name, company) {
  return name + ' works at ' + company;
});

// 2. Ask librarySystem to return our 'workBlurb' library, which depends on
// the 'name' and 'company' libraries.

librarySystem('workBlurb'); // 'Gordon works at Watch and Code'