solution to Watch and Code challenge #1: 'librarySystem with dependencies'

beasts01.js

// v1 attempt
// This version passes all tests. However, it's missing a couple of key features:
// (1) it only takes one 'level' of dependencies (no nested dependencies), and
// (2) dependencies must have already been loaded in order for a library to be loaded.

(function() {
  var libraryStorage = {};

  function librarySystem(libraryName, dependencyArray, callback) {
    if (arguments.length > 1) {
      var callbackArgs = [];

      if (dependencyArray.length) {
        callbackArgs = dependencyArray.map(function(dependencyName) {
          return libraryStorage[dependencyName];
        });
      }

      libraryStorage[libraryName] = callback.apply(null, callbackArgs);
    } else {
      return libraryStorage[libraryName];
    }
  }

  window.librarySystem = librarySystem;
})();


// v2 attempt
// This version adds support for nested dependencies, as well as for adding
// libraries and dependencies in any order (i.e., you can add a library even
// if that library's dependencies have not yet been added).

(function() {
  var libraryStorage = {};

  function librarySystem(libraryName, dependencyArray, callback) {
    if (arguments.length > 1) {
      libraryStorage[libraryName] = {
        library: callback,
        dependencies: dependencyArray
      };
    } else {
      return loadNestedDependencies(libraryName);
    }
  }

  function loadNestedDependencies(libraryName) {
    var dependencies = [];

    if (libraryStorage[libraryName].dependencies.length) {
      dependencies = libraryStorage[libraryName].dependencies.map(function(dependencyName) {
        return loadNestedDependencies(dependencyName);
      });
    }

    return libraryStorage[libraryName].library.apply(null, dependencies);
  }

  window.librarySystem = librarySystem;
})();




// testing library addition prior to dependency addition

librarySystem('app', ['router'], function(router) {
  return {
    description: 'Just a silly app that has a dependency',
    dependencies: [arguments]
  };
});

librarySystem('router', [], function() {
  return {
    description: 'Supposedly, I can handle app routing.',
    dependencies: [arguments]
  };
});

console.log(librarySystem('app'));

// testing nested dependencies

librarySystem('dependency', ['app2'], function(app2) {
  return 'loaded dependency with ' + app2;
});

librarySystem('app2', [], function(dependency) {
  return 'app2';
});

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

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

very well done!!!