Refactoring JavaScript Applications
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This document discusses refactoring a legacy JavaScript application. It begins with motivation for refactoring a 6 year old Java application with over 20,000 lines of JavaScript code. It then discusses questions around whether refactoring JavaScript is necessary, defines what refactoring is, and provides an example refactored application. The document outlines 5 versions of refactoring the sample application, including inverting dependencies with RequireJS, improving design with model objects and unit tests, managing dependencies with Bower, improving design further with MVP pattern, and automating tasks with Grunt. It concludes by discussing taking refactoring further with CoffeeScript and related literature.
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Refactoring JavaScript Applications
- 1. codecentric d.o.o Jovan Vidić, IT Consultant @ codecentric Refactoring Java Script Applications
- 2. Motivation Should We Refactor JavaScript? Refactoring Sample Application Beyond Refactoring Agenda
- 3. ~ 6 years of development Java + DWR 732 JavaScript files ~ 20 000 lines of javascript code Motivation - Legacy project
- 4. What was wrong? - JavaScript in HTML - Global functions - Inline styles - No coding style guidelines - No tests MOTIVATION - Legacy project
- 5. What was OK? - OOP - Throwing own errors - Wrapping third party libraries - Prototype.js MOTIVATION - Legacy project
- 6. Should We Refactor JavaScript ?
- 7. “It is not necessary to change. Survival is not mandatory” W. Edwards Deming W E Deming
- 9. What is Refactoring? a change made to the internal structure of software to make it easier to understand and cheaper to modify without changing its observable behavior M. Fowler
- 10. This is not refactoring
- 11. agile manifesto 8th principle Agile processes promote sustainable development. The sponsors, developers, and users should be able to maintain a constant pace indefinitely.
- 12. Refactoring Sample Application – v1 – index.html </head>! <body>! <ul class="nav nav-pills">! <li class="active"><a href="../../v1/client/index.html">V1</a></ li>! <li><a href="../../v2/client/index.html">V2</a></li>! <li><a href="../../v3/client/index.html">V3</a></li>! <li><a href="../../v4/client/index.html">V4</a></li>! <li><a href="../../v5/client/index.html">V5</a></li>! </ul>! <div class="page-header">! <h1>Coding Serbia <small> Refactoring JavaScript Applications - V1</small></h1>! </div>! <!-- Button trigger modal -->! <button class="btn btn-primary btn-lg" data-toggle="modal" onclick="createSpeaker()">! Add Speaker! </button>!
- 13. <script src="js/jquery.min.js"></script>! <script src="js/bootstrap.min.js"></script>! <script src="js/speakers.js"></script>! ! <script type="text/javascript">! load();! </script>! </body>! Refactoring Sample Application – v1 – index.html
- 14. Refactoring Sample Application – v1 – speakers.js function add() {! var speakerId = $('#speakerId').val();! ! $.ajax({! type: speakerId == '' ? "POST" : "PUT",! url: speakerId == '' ? "http://localhost:4730/speakers" : "http:/! data: JSON.stringify({id: speakerId, firstName: $('#firstName').v! contentType: "application/json; charset=utf-8",! dataType: "json",! success: function(data){ $('#speakerId').val(''); $('#firstName’)! failure: function(errMsg) {alert(errMsg);}! ! function load() {! $.getJSON( "http://localhost:4730/speakers", function( data ) {! var newRows = "";! $.each(data, function(i,item) {! var sessionTime = new Date(Date.parse(item.sessionTime));! ! newRows += "<tr><td>" + sessionTime.toLocaleString() +"</td><! });! $(".table-striped tbody").html("");! $(".table-striped tbody").append(newRows);! });! };!
- 15. Refactoring Sample Application – v1 It is a complete mess! How should I start?
- 16. Refactoring Sample Application – v1 – selenium
- 17. Refactoring Sample Application – v1 What about JSLint/JSHIT?
- 18. It will scream at you!
- 19. Refactoring Sample Application – v2 Invert dependencies
- 20. Refactoring Sample Application – v2 - REQUIREJS requirejs.config({! paths: {! "jquery": "lib/jquery.min",! "bootstrap": "lib/bootstrap.min"! },! shim: {! "bootstrap": {! deps: ["jquery"]! }! }! });! ! require(["app/speakers","bootstrap"], function (speakers) {! ! $("#btnSaveSpeaker").click(function() {! speakers.save();! });! ! speakers.loadAll();! });! <script data-main="scripts/main" src="scripts/lib/require.js"></script>!
- 21. Refactoring Sample Application – V2 – SPEAKERS.JS & THEME.jS define(["jquery","app/theme"], function ($, theme) {! "use strict";! ! var SpeakerControler = {! loadAll : function () {! $.getJSON("http://localhost:4730/speakers", function (data) {! var speakersTable = $("." + theme.SPEAKERS_TABLE +" tbody") define([], function () {! "use strict";! ! return {! DELETE_BUTTON : "btn btn-danger glyphicon glyphicon-remove",! EDIT_BUTTON : "btn btn-default glyphicon glyphicon-pencil",! SPEAKERS_TABLE : "table-striped"! };! });!
- 22. Refactoring Sample Application – SPEAKERS.JS define(["jquery","app/theme"], function ($, theme) {! "use strict";! ! var SpeakerControler = {! loadAll : function () {! cell.append($("<button class='"+theme.DELETE_BUTTON+"'></button>”)! SpeakerControler.remove(item.id);! })); remove : function(id) {! $.ajax({! type: "DELETE",! url: "http://localhost:4730/speaker/" + id,! success: function() {! SpeakerControler.loadAll();! }! });! }! return SpeakerControler;! });
- 23. My code is isolated now Can I write unit tests?
- 25. Refactoring Sample Application – v3 Manage dependencies
- 26. Refactoring Sample Application – v3 – bower.json {! "name": "javascript-refactoring",! "version": "1.0",! "authors": [! "Jovan Vidic <jovan.vidic@codecentric.de>"! ],! "private": true,! "ignore": [! "node_modules",! "bower_components",! "test",! "tests"! ],! "dependencies": {! "jquery": "1.11.1",! "bootstrap" : "3.2.0",! "requirejs" : "2.1.15"! },! ! "devDependencies": {! ! }! }!
- 27. Refactoring Sample Application – v4 Improve design Introduce model objects & unit tests
- 28. Refactoring Sample Application – v4 – MODEL.JS function Speaker(id, firstName, lastName, topic, sessionTime, track) {! this.id = id;! this.firstName = firstName;! this.lastName = lastName;! this.topic = topic;! this.sessionTime = sessionTime;! this.track = track;! ! this.hasId = function () {! return (this.id !== undefined) && (this.id !== null) ! && (this.id !== "");! };! ! this.getFullName = function () {! return this.firstName + " " + this.lastName;! };! }! ! return {! "Agenda" : {! "Speaker" : Speaker! }! };!
- 29. Refactoring Sample Application – v4 – Speakers.JS define(["jquery", "app/model", "app/theme"], function ($, model, theme) {! "use strict";! var SpeakerControler = {! editSpeaker : function(id) {! $.getJSON( "http://localhost:4730/speaker/" + id, ! function(speakerData) {! if(speakerData) {! var speaker = convertToModel(speakerData);! showEditSpeakerPopup(speaker);! }! });! }! function showEditSpeakerPopup(speaker) {! $('#myModalLabel').html('Edit speaker <strong>' ! + speaker.getFullName() + "</strong>");! }! function convertToModel(speakerData) {! return new model.Agenda.Speaker(speakerData.id, speakerData.firstName, speakerData.lastName, speakerData.topic, speakerData.sessionTime, speakerData.track);! }
- 30. Refactoring Sample Application – v4 – jasmine describe("Test model objects", function() {! "use strict";! ! var Model;! ! beforeEach(function(done) {! require(["app/model"], function (model) {! Model = model;! done();! });! }); it("should return Jovan Vidic when firstName is Jovan and lastName is Vidic", function() {! ! var speaker = new Model.Agenda.Speaker(1, "Jovan", "Vidic");! ! expect(speaker.getFullName()).toBe("Jovan Vidic");! });!
- 31. Refactoring Sample Application – v4 That's all cool but my code still stinks?!
- 32. Trust me I've been there
- 33. Refactoring Sample Application – v5 Improve design & automate
- 34. Refactoring Sample Application – v5 – SPEAKERS AJAX CLIENT define(["jquery", "app/model"], function ($, model) {! "use strict";! ! var baseURL = requirejs.s.contexts._.config.cs["api-url"],! speakersURL = baseURL + "speakers/",! speakerURL = baseURL + "speaker/";! ! function convertToModel(speakerData) {! return new model.Agenda.Speaker(speakerData.id, speakerData.firstNa }! return {! loadAllSpeakers : function (callbackHandle) {! $.getJSON(speakersURL, function (speakersData) {! var speakers = [];! $.each(speakersData, function (index, speakerData) {! var speaker = convertToModel(speakerData);! speakers.push(speaker);! });! callbackHandle.success(speakers);! });! },
- 35. Refactoring Sample Application – v5 – Backend FACADE define(["app/client/speakers_ajax_client"], function (speakersClient) {! "use strict";! ! return {! loadAllSpeakers : function (callbackHandle) {! speakersClient.loadAllSpeakers(callbackHandle);! },! ! saveSpeaker : function (speaker, callbackHandle) {! speakersClient.saveSpeaker(speaker, callbackHandle);! }!
- 36. Refactoring Sample Application – v5 - TesTS define(["squire"], function (Squire) {! "use strict";! ! var injector = new Squire(),! client = jasmine.createSpyObj("client", ["loadAllSpeakers", "saveSpeaker", "removeSpeaker"]),! callbackHandle = jasmine.createSpy("callback"),! builder = injector.mock("app/client/speakers_ajax_client”, client); ! describe("Test backend facade", function() {! ! var backend;! ! beforeEach(function(done) {! builder.require(["app/backend_facade"], function(backendFacade) backend = backendFacade;! done();! });! });! it("should loadAllSpeakers", function() {! backend.loadAllSpeakers(callbackHandle);! expect(client.loadAllSpeakers)! .toHaveBeenCalledWith(callbackHandle);! });! ! !
- 37. Refactoring Sample Application – v5 - MVP http://warren.chinalle.com/2010/12/18/model-view-presenter/
- 38. Refactoring Sample Application – v5 – speakers PRESENTER define(["app/backend_facade", "app/speakers/speakers_view", ! "app/events"], function (backend, SpeakersView, events) {! ! "use strict";! ! var EventManager = events.EventManager,! Actions = events.Actions;! ! function SpeakerPresenter() { ! var view = new SpeakersView(),! self;! ! return {! init : function () {! self = this;! EventManager.register(Actions.LOAD_ALL_SPEAKERS, this.loadAll);! },! loadAll : function () {! backend.loadAllSpeakers({! "success" : function (speakers) {! view.showAll(speakers);! }! });! },!
- 39. Refactoring Sample Application – v5 – Speakers view define(["app/events", "app/components", "app/speakers/speakers_popup"], ! "use strict”;! var EventManager = events.EventManager;! ! function SpeakersView() {! var speakersTable = new components.SpeakersTable(),! createButton = new components.Button("btnAddSpeaker"),! popup = new SpeakersPopup();! ! function showCreateSpeakerDialog() {! EventManager.fire(events.Actions.SHOW_CREATE_SPEAKER);! }! function init() {! createButton.addClickListener(showCreateSpeakerDialog);! }! init();! return {! showAll : function (speakers) {! var i, len;! speakersTable.clear();! for (i = 0, len = speakers.length; i < len; i += 1) {! speakersTable.addSpeaker(speakers[i]);! }! }!
- 40. Refactoring Sample Application – v5 – SPEAKERS POPUP define(["app/model", "app/events", "app/components"], function (model, even ! function SpeakersPopup() {! var speaker,! popup = new components.Popup("myModal"),! firstNameInput = new TextField("firstName"),! ! function saveSpeaker() {! speaker.firstName = firstNameInput.val();! speaker.lastName = lastNameInput.val();! speaker.topic = topicInput.val();! ! if (speaker.hasId()) {! EventManager.fire(events.Actions.EDIT_SPEAKER, speaker);! } else {! EventManager.fire(events.Actions.SAVE_SPEAKER, speaker);! }! }! return {! openAndSet : function (speakerToUpdate) {! speaker = speakerToUpdate;! firstNameInput.val(speaker.firstName);! lastNameInput.val(speaker.lastName);! !
- 41. Refactoring Sample Application – v5 – components http://warren.chinalle.com/2010/12/18/model-view-presenter/ define(["jquery", "app/events", "app/theme"], function ($, events, theme) ! function TextField(id) {! var textField = $("#" + id);! return {! val : function (value) {! if (value !== undefined) {! textField.val(value);! } else {! return textField.val();! }! }! };! }! ! function SimpleButton(id) {! var button = $("#" + id);! return {! addClickListener : function (listener) {! button.click(listener);! }! };! }! !
- 42. For the win
- 43. Refactoring Sample Application – v5 - GRUNT grunt.initConfig({! ! jslint: {! src: [! "scripts/**/*.js"! ],! ! },! ! karma: {! unit: {! configFile: "karma.conf.js"! }! },! ! copy: {! main: {! files: [! {expand: true, src: ["lib/bootstrap/dist/css/**"], dest: "dist/"},! {expand: true, src: ["lib/bootstrap/dist/fonts/**"], dest: "dist/"} {expand: true, src: ["lib/requirejs/require.js"], dest: "dist/"}! ]! }! }!
- 44. Refactoring Sample Application – v5 - GRUNT requirejs: {! compile: {! options: {! baseUrl: "scripts/",! name: "main",! out: "dist/app-built.js”,! paths: {! app: "app/",! "jquery": "../lib/jquery/dist/jquery.min",! "bootstrap": "../lib/bootstrap/dist/js/bootstrap"! }! }! }! },! processhtml: {! options: {! data: { ! }! },! dist: {! files: {! "dist/index.html": ["index.html"]! }! }!
- 46. Coffeescript define [], () ->! ! class Speaker! constructor: (@id, @firstName, @lastName, @topic, @sessionTime, @track) ->! ! hasId: ->! @id?.length != 0! ! fullName: ->! @firstName + " " + @lastName! ! return {"Agenda": {"Speaker" : Speaker}} !
- 47. Literature