Module definition function with namespace and dependencies

module.js

// -----------------------------------------------------------------------------
// Copyright (c) 2018 Jakub Jankiewicz
// Released under MIT license
//
// generic namespace generator the constructor should declare private functions
// and variables and return public api, the module is created when all dependecies
// are resolved (all modules are created)
//
// @param namespace dot separated namespace that will be added to window object
// @param dependencies array of string (dependencies) can be empty array
// @param constructor function that should return public module API
//
// usage:
// module('app.projects', ['app.helpers'], function(helpers) {
//     console.log(app.helpers === helpers);
//     helpers.log('hello');
//     return {
//         foo: function() {
//             helpers.log('foo');
//         }
//     };
// });
// module('app.helpers', [], function() {
//     return {
//         log: function(msg) {
//             console.log(msg);
//         }
//     };
// });
// -----------------------------------------------------------------------------
var module = (function() {
  // to keep track of dependencies, real objects are nested in window
  var modules = {};

  // ---------------------------------------------------------------------------
  function init(module) {
    var dependencies = module.dependencies.map(function(name) {
      if (!modules[name]) {
        throw new Error('Internal Error: module ' + name + ' not defined when' +
                        ' initializing ' + module.name);
      }
      return modules[name].module;
    });
    module.loaded = true;
    Object.assign(module.module, module.constructor.apply(null, dependencies));
  }
  // ---------------------------------------------------------------------------
  function concat(array) {
    array = array.slice()
    if (array.length > 1) {
      var last = array.pop();
      return array.join(', ') + ' and ' + last;
    } else {
      return array[0];
    }
  }
  // ---------------------------------------------------------------------------
  return function module(namespace, dependencies, constructor) {
    var names = namespace.split('.');
    var current = window;
    names.forEach(function(name) {
      if (!current[name]) {
        current[name] = {};
      }
      current = current[name];
    });
    if (modules[namespace]) {
      throw new Error('Module ' + namespace + ' already defined');
    }
    var module = modules[namespace] = {
      name: namespace,
      module: current,
      dependencies: dependencies,
      constructor: constructor
    };
    // if dependencies not resolved
    if (dependencies.length) {
      // are all dependentant modules loaded?
      var foundDepenencies = dependencies.filter(function(dependency) {
        return modules[dependency];
      });
      if (foundDepenencies.length === dependencies.length) {
        init(module);
      }
    } else {
      // no depeendecies
      init(module);
    }
    var modulesWithdependencies = Object.keys(modules).filter(function(name) {
      var module = modules[name];
      // don't process self and modules that don't have dependencies,
      // those was already loaded
      return Object.keys(module.dependencies).length;
    });

    modulesWithdependencies.filter(function(name) {
      return name !== namespace;
    }).forEach(function(name) {
      var module = modules[name];
      var dependats = module.dependencies;
      var resolved = dependats.filter(function(key) {
        return modules[key];
      });
      // init modules that have resolved dependencies
      if (resolved.length === dependats.length) {
        if (!module.loaded) {
          init(module);
        }
      } else {
        // find mutual dependencies
        if (dependats.length) {
          var mutualDependant = modulesWithdependencies.filter(function(searchName) {
            var searchModule = modules[searchName];
            return Object.keys(searchModule.dependencies).indexOf(name) !== -1;
          });
          if (mutualDependant.length) {
            var brokenModules = mutualDependant.concat([name]);
            // this will show error in toaster and log in server because of window
            // error handler in error.js
            throw new Error(concat(brokenModules) + ' have mutual dependecy');
          }
        }
      }
    });
  };
})();