Refactor existing code

data/content-scripts/settings.js

+/**
+ * Application settings content script.
+ *
+ * @module content-scripts/settings
+ */
+
+'use strict';
+
 /**
  * Fires once the content script worker is initialized.
  *
- * @event worker:initialized
  * @param {Object} initialState The initial state of the settings module.
+ * @listens main/worker:initialized
  */
 self.port.once('worker:initialized', function (initialState) {
 
     applyL10n(initialState.l10n);
 });
 
+/**
+ * Fires once a preference has been fetched.
+ *
+ * @param {Object} preference The externally fetched preference.
+ * @listens main/preference:fetched
+ */
 self.port.on('preference:fetched', function () {
-
     // TODO Re-render the user interface.
 });
 
@@ -18,8 +31,8 @@ self.port.on('preference:fetched', function () {
  * Applies a given localization to marked document elements.
  * https://bugzilla.mozilla.org/show_bug.cgi?id=787351
  *
- * @private
  * @param {Object} l10n A localization object.
+ * @private
  */
 function applyL10n (l10n) {
 
@@ -35,15 +48,22 @@ function applyL10n (l10n) {
     });
 }
 
+/**
+ * Fetch preference event emitter.
+ *
+ * @event preference:fetch
+ * @property {String} preferenceKey The key of the requested preference.
+ */
 function fetchPreference (preferenceKey) {
     self.port.emit('preference:fetch', preferenceKey);
 }
 
 /**
- * Emitters
+ * Preference changed event emitter.
+ *
+ * @event preference:changed
+ * @property {Object} preference The updated preference.
  */
-
-self.port.emit('preference:changed', {
-    key: 'sliderPosition',
-    value: 2
-});
+function preferenceChanged (preference) {
+    self.port.emit('preference:changed', preference);
+}

src/main.js

 /**
- * Main
+ * Application entry point.
+ *
+ * @module main
  */
 
 'use strict';
 
 /**
- * Imports
+ * Simplifies the process of obtaining browser service references.
+ *
+ * @var {Object} Services
  */
-
 var { Services } = require('resource://gre/modules/Services.jsm');
 
+/**
+ * Can be used to get localization entries by key name.
+ *
+ * @var {function} _
+ */
 var _ = require('sdk/l10n').get;
-var pageMod = require('sdk/page-mod');
-var self = require("sdk/self");
 
 /**
- * Constants
+ * Facilitates running scripts in the context of web pages.
+ *
+ * @var {Object} pageMod
  */
+var pageMod = require('sdk/page-mod');
 
-const BROWSER_NAME = 'Orfox';
+/**
+ * Provides access to extension metadata.
+ *
+ * @var {Object} self
+ */
+var self = require("sdk/self");
 
 /**
- * Variables
+ * The browser's chrome window object.
+ *
+ * @var {Object} chromeWindow
  */
+var chromeWindow = Services.wm.getMostRecentWindow('navigator:browser');
 
-var browserWindow = Services.wm.getMostRecentWindow('navigator:browser');
-var browserWindowIdentifier = null;
+/**
+ * Uniquely identifies the extension's chrome menu item.
+ *
+ * @var {Number} chomeMenuItemIdentifier
+ */
+var chromeMenuItemIdentifier = null;
 
 /**
- * Public Functions
+ * The name of the target browser.
+ *
+ * @constant BROWSER_NAME
+ * @type {String}
+ * @default
  */
+const BROWSER_NAME = 'Orfox';
 
+/**
+ * Executed as soon as the add-on is loaded.
+ */
 exports.main = function () {
 
     pageMod.PageMod({
@@ -40,11 +69,12 @@ exports.main = function () {
         onAttach: startListening
     });
 
-    browserWindowIdentifier = browserWindow.NativeWindow.menu.add({
+    // Add the extension's chrome menu item to the main browser menu.
+    chromeMenuItemIdentifier = chromeWindow.NativeWindow.menu.add({
         name: _('settings_label', BROWSER_NAME),
         callback: function () {
 
-            var tabBrowser = browserWindow.BrowserApp;
+            var tabBrowser = chromeWindow.BrowserApp;
 
             tabBrowser.addTab('chrome://tor-browser-settings/content/settings.html', {
                 selected: true,
@@ -55,16 +85,20 @@ exports.main = function () {
     });
 };
 
+/**
+ * Executed when the add-on is unloaded.
+ */
 exports.onUnload = function () {
 
     // Clean up add-on state.
-    browserWindow.NativeWindow.menu.remove(browserWindowIdentifier);
+    chromeWindow.NativeWindow.menu.remove(chromeMenuItemIdentifier);
 };
 
 /**
- * Private Functions
+ * Executed as soon as a content script has been attached to a page.
+ *
+ * @param {Object} worker Allows for direct communication with content scripts.
  */
-
 function startListening (worker) {
 
     worker.port.emit('worker:initialized', {