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Mastering Large Scale
JavaScript Applications
Fabian Jakobs
About



•   Senior JavaScript Developer at 1&1

•             core developer since 2006


               @fjakobs
Man With Two Hats
Framework   Application
Large Scale
JavaScript Applications
JavaScript Application
JavaScript Application
JavaScript Application
JavaScript Application
JavaScript Application

•   Single Page Application

•   Client Logic in JavaScript

•   Client-Server
    Communication with
    AJAX calls
Large Scale

• Complexity and Size of JavaScript code
 • ~ 150,000 LOC
 • ~ 1000 Classes
• Rich Web Mail Application

• Pure JavaScript Client
• Backend Communication with Ajax calls
• Based on qooxdoo
• Client-side JavaScript Framework
• Cross-browser web applications
• Open Source
JavaScript isn‘t made for this
JavaScript isn‘t made
         for this
• No package mechanism
• By default everything is in the global
  namespace
• Only basic building blocks for OOP
• Tooling still sucks
Everybody puts a layer
       on top
• GWT covers JavaScript with Java
• Cappuchino uses Objective-J
• Adobe invented ActionScript
• Everyone else uses (different) meta object
  systems written in JavaScript
qooxdoo OOP
qx.Class.define("demo.Person",
{
  extend : qx.core.Object,

  construct : function(firstName, lastName)
  {
	     this.base(arguments);	
	
	     this._firstName = firstName;
	     this._lastName = lastName;
  },

  members :
  {
    getFullName : function() {
      return this._firstName + " " + this._lastName;
    }
  }
});
Tooling
Tooling

  API Doc                    Unit Testing
                  Linker
Auto Completion            Code Coverage
                    Lint


         IDE Support
Tooling dilemma
• Different OOP syntax makes generic
  tooling hard
• Tools often depend in certain Framework
  features


• Don‘t just look at the widgets, look at the
  development tools as well
Find the Right Level of
      Abstraction
Desktop Like Web
 Applications Need
Desktop Abstractions

• Widgets               • DOM Nodes
• Layout Manager   vs   • CSS
• Themes                • Browser Bugs
Abstractions
                            Application
  Application Components

      Custom Widgets


       Base Widgets         Framework
         UI Core
     (Rendering Engine)

 BOM (Cross Browser Code)

   Core (JavaScript OOP)
Desktop Style
       Development Model

// Create a button
var button = new qx.ui.form.Button("First Button", "demo/browser.png");

// Add button to container at fixed coordinates
container.add(button, {left: 100, top: 50});

// Add an event listener
button.addListener("execute", function(e) {
  alert("Hello World!");
});
Leaky Abstractions
• Emulated behavior may be slower
 • e.g. Canvas wrapper for IE
• For advanced tasks its essential to know
  the lower layers
  • CSS, HMTL, DOM knowledge is still
    needed
Styling
Styling
No OS clone!   No default theme   Everything Custom!
Not Everyone
Speaks German
i18n
i18n
i18n
i18n in qooxdoo
this button = var qx.ui.form.Button(this.tr("Hello World!"));




      • Standards
       • gettext
       • CLDR
      • good external tooling
      • known by professional translators
Performance
Our Bottlenecks

• Startup time
• Widget creation
• Table scroll performance
Startup Time
  The 3Cs + O


  • Combine
  • Compress
  • Cache
  • On demand
Combine

• reduce number of requests
• combine                  JS        JS   PNG     PNG
 • JavaScript files
 • CSS                          JS              PNG
 • Images
Compress

• optipng et el for images
• compress JavaScript
• serve with gzip
Compress JavaScript
Cache

• Serve static files with „cache forever“
 • Increase version number if content
    changes
• Use Image servers
On Demand

• Defer operations
 • Load Code on demand
 • Load Data on demand
 • Render UI on demand
On Demand Code

• The initial view does not need
 • Editor
 • Settings
 • Address book
 • ...
On Demand Code
   • Code
qx.io.PartLoader.require("settings", function()
{
  mailclient.ui.SettingsDialog.getInstance().open();
}, this);



   • Content
...
"packages" : {
  "parts" : {
    "settings": {
      "include" : ["mailclient.ui.SettingsDialog"]
    }
  }
}
...
On Demand Data and UI

• Thousands of mails
  in the inbox
• Only load visible
  data
• Only render visible
  rows of the table
Widget Creation
• DOM operations are expensive
• Creation Widgets is expensive
• Reuse Widgets
 • Share Widgets
 • Pool Widgets
• Increases Complexity!
Reuse Widgets



pool and reuse               share mail preview
  mail folder                   among tabs
Clean Code
Decouple UI
Components
Decouple UI
Components




   Message Bus
Code Should be
Executable in Isolation

• Without rebuilding the application
• Without restarting the application
• Without a server
Unit Tests
Mini Applications
Summary

• Good Abstractions
• Styling
• Internationalization
• Performance
• Clean Code
colorstrip.gifT
THE NEW ERA OF WEB DEVELOPMENT




Thank you.

                                Fabian Jakobs
                                    @fjakobs
                <fabian.jakobs@1und1.de>
                         http://qooxdoo.org
Fotos
•   http://www.flickr.com/photos/martin_uj/2505238011/

•   http://www.flickr.com/photos/born-clothing/3764261653/

•   http://www.flickr.com/photos/countrushmore/540548338/

•   http://www.flickr.com/photos/gordonr/42555739/

•   http://www.flickr.com/photos/evaekeblad/345203452/

•   http://www.flickr.com/photos/oldonliner/1095360979/

•   http://www.flickr.com/photos/imcomkorea/3496427357/

•   http://www.flickr.com/photos/nhr/460382116/

•   http://www.flickr.com/photos/evaekeblad/345203452/

Masterin Large Scale Java Script Applications