Watch and Code - Beasts 4. librarySystem with dependencies

libraryWithDependencySystem.js

(function(){
    // build a storage for libraries
    var libraryStorage = {};

    function librarySystem(libraryName, dependencyArray, callback){
        // when has dependencyArray and callback
        if(arguments.length > 1){
            // when has dependency
            if(dependencyArray.length > 0){
                // save the content of dependency in an array
                var contentOfDependency = dependencyArray.map(function(x){return librarySystem(x)});
                // pass content of dependency as callback's argument
                // save the library's name and content in the libraryStorage
                libraryStorage[libraryName] = callback.apply(this, contentOfDependency);
            // when no dependency
            } else {
                // save the library's name and content in the libraryStorage
                libraryStorage[libraryName] = callback();
            }
        // when no dependencyArray and callback
        } else {
            // return library's content
            return libraryStorage[libraryName];
        }
    }

    // make librarySystem accessable globally
    window.librarySystem = librarySystem;
})();