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LARGE-SCALE
USING JAVASCRIPT AND JQUERY
BUILDING
WITH @ADDYOSMANI
APPLICATIONS
#JQCON #LARGESCALE
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I WORK AT A COMPANY
CALLED
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BUILDING JAVASCRIPT APPS THAT
HAVE TO SCALE FROM THE GET-GO
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WHAT DOES THAT INVOLVE?
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DECOUPLING
BASIC CONCEPTS
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SEPARATES UNITS OF CODE THAT
DON’T DEPEND ON EACH OTHER
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FILTER
FORMULA EDITOR
GRID
SPREADSHEET
WIDGET/MODULE
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PROMOTES REUSABILITY
LESS COUPLING = EASIER REUSE
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BUT THAT’S NOT ALL!
DECOUPLING CAN BE TAKEN
FURTHER
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REDUCING THE RISK OF BREAKAGE
WHEN OTHER MODULES FAIL
EXAMPLE
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COUPLED, DIRECT CALLS
//Coupled
$.when( $.ajax("mail.php") )
.then(function( ajaxArgs ){
var jqXHR = ajaxArgs[2],
data = jqXHR.responseText;
// Display notification and preview
modals.show('New Message', data);
// What happens if something breaks here?
// Play new message sound
audioManager.play('newMessage');
// Update the unread message count
messages.increaseMessageCount('unread');
});
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DECOUPLED, EVENT-DRIVEN
// Decoupled, Event-driven
$.when( $.ajax("mail.php") )
.then(function( ajaxArgs ){
var jqXHR = ajaxArgs[2],
data = jqXHR.responseText;
// Tell the application there is a new message, share the data
$.publish('newMessage', data);
// Other modules can now just listen out for 'newMessage'
});
$.subscribe('newMessage', ...); // modals.show()
// How about now?
$.subscribe('newMessage', ...); // audioManager.play()
$.subscribe('newMessage', ...); // messages.increaseMessageCount()
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PUB/SUB
BASIC CONCEPTS
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LOGICALLY DECOUPLE OBJECTS
GENERATING EVENTS
FROM THOSE REACTING
TO THEM
NEW MESSAGE
‘HELLO WORLD’
THERE’S A NEW
MESSAGE!
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BAKED INTO MVC, MV*
MODELS VIEWS CONTROLLERS
MODELS CAN BE OBSERVED FOR CHANGES
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OPTION 1: JQUERY CUSTOM EVENTS
$(document).trigger('eventName');
//equivalent to $.publish('eventName')
$(document).on('eventName',...);
//equivalent to $.subscribe('eventName',...)
// Example:
$(document).on('newMessage', function(){
displayNewMailNotification();
});
$(document).trigger('newMessage');
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OPTION 2: PUB/SUB WRAPPER
// Using .on()/.off() from jQuery 1.7.1
(function($) {
var o = $({});
$.subscribe = function() {
o.on.apply(o, arguments);
};
$.unsubscribe = function() {
o.off.apply(o, arguments);
};
$.publish = function() {
o.trigger.apply(o, arguments);
};
}(jQuery));
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OPTION 3: $.CALLBACKS
// Multi-purpose callbacks list object
// Pub/Sub implementation:
var topics = {};
jQuery.Topic = function( id ) {
var callbacks,
topic = id && topics[ id ];
if ( !topic ) {
callbacks = jQuery.Callbacks();
topic = {
publish: callbacks.fire,
subscribe: callbacks.add,
unsubscribe: callbacks.remove
};
if ( id ) {
topics[ id ] = topic;
}
}
return topic;
};
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OPTION 3: $.CALLBACKS
// Usage:
// Subscribers
$.Topic( 'mailArrived' ).subscribe( fn1 );
$.Topic( 'mailArrived' ).subscribe( fn2 );
$.Topic( 'mailSent' ).subscribe( fn1 );
// Publishers:
$.Topic( 'mailArrived' ).publish( 'hello world!' );
$.Topic( 'mailSent' ).publish( 'woo! mail!' );
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OPTION 4: BACKBONE.JS EVENTS
var myObject = {};
_.extend( myObject, Backbone.Events );
myObject.on('eventName', function( msg ) {
console.log( 'triggered:' + msg );
});
myObject.trigger('eventName', 'some event');
// Similarly..
person.on('change:name change:age', function( msg ) {
console.log('name and age changed');
});
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CHECK-UP
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YOUR CURRENT ARCHITECTURE
MODULES
WIDGETS
MVC
LIBRARIES
TOOLKITS
APPLICATION CORE
TEMPLATES
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IF ONE PART OF YOUR APPLICATION
BREAKS
CAN THE APP FIX THIS BREAK ITSELF?
BUT THERE ARE PROBLEMS:
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HOW MUCH OF WHAT
WE CREATE IS
EASILY REUSABLE?
HOW SECURE IS
YOUR APPLICATION
FROM ITSELF?
CAN OUR MODULES
BE TESTED
INDEPENDENTLY?
MORE PROBLEMS
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THINK LONG TERM!
WHAT HAVEN’T YOU
FACTORED IN YET?
WHAT MIGHT CHANGE?
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“THE SECRET TO BUILDING LARGE APPS IS NEVER BUILD
LARGE APPS. BREAK YOUR APP INTO SMALL PIECES. THEN,
ASSEMBLE THOSE TESTABLE, BITE-SIZED PIECES INTO YOUR
BIG APPLICATION”
- JUSTIN MEYER
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PATTERNS
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FACADE PATTERN
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SIMPLIFIES USAGE OF A MODULE
THROUGH A LIMITED API
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$( el ).css()
$( el ).animate(..)
$( el ).attributes( key, value )
...
EXAMPLES YOU USE ALL THE TIME
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HIDES IMPLEMENTATION
LEVEL DETAILS
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var module = (function() {
var _private = {
i:5,
get : function() {
console.log('current value:' + this.i);
},
set : function( val ) {
this.i = val;
},
run : function() {
console.log('running');
},
jump: function(){
console.log('jumping');
}
};
return {
facade : function( args ) {
_private.set(args.val);
_private.get();
if ( args.run ) {
_private.run();
}
}
}
}());
module.facade({run: true, val:10}); //outputs current value: 10, running
A limited API allowing access to
a more complex implementation
FACADE IMPLEMENTATION
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return {
facade : function( args ) {
// set values of private properties
_private.set(args.val);
// test setter
_private.get();
// optional: provide a simple interface
// to internal methods through the
// facade signature
if ( args.run ) {
_private.run();
}
}
}
module.facade({run: true, val:10});
Users are only
concerned with using
the facade
FACADE IMPLEMENTATION
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ENABLES COMPLEXITY BEHIND
THE SCENES
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bindReady: function() {
...
// One snippet for event listeners in jQuery core where the user
// isn't exposed to any of the cross-browser implementation
// handling behind the scenes
if ( document.addEventListener ) {
// Use the handy event callback
document.addEventListener( "DOMContentLoaded",DOMContentLoaded,
false );
// A fallback to window.onload, that will always work
window.addEventListener( "load", jQuery.ready, false );
// If IE event model is used
} else if ( document.attachEvent ) {
document.attachEvent( "onreadystatechange", DOMContentLoaded);
and another
.bindReady() used for $(document).ready()
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MEDIATOR PATTERN
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TOWER HANDLES
WHAT PLACES CAN
TAKE OFF OR LAND
ALL COMMUNICATION
DONE FROM PLANES TO
TOWER, NOT PLANE TO
PLANE
A CENTRALISED
CONTROLLER IS KEY TO
SUCCESS HERE
ANALOGY: AIR TRAFFIC CONTROL
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ALLOWS MODULES TO BROADCAST
OR LISTEN FOR NOTIFICATIONS
A MEDIATOR:
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var mediator = (function(){
var subscribe = function(channel, fn){
if (!mediator.channels[channel])mediator.channels[channel] = [];
mediator.channels[channel].push({ context: this, callback:fn });
return this;
},
publish = function(channel){
if (!mediator.channels[channel]) return false;
var args = Array.prototype.slice.call(arguments, 1);
for (var i = 0, l = mediator.channels[channel].length; i
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// Publish-Subscribe via a centralised mediator
mediator.subscribe('messageReceived', function( data ){
// Awesome! a new message
// I can do something with the data
});
mediator.publish('messageReceived', {
sender: '[email protected]',
preview: 'hello world'
});
MEDIATOR EXAMPLE:
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NOTIFICATIONS CAN BE HANDLED
BY ANY NUMBER OF MODULES
CENTRALISED PUB/SUB
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MESSAGES
CHAT
NOTIFICATIONS
A new message is
available
A new
notification has
been posted
Any new emails?
Paul sent a new IM
Any new instant
messages?
Are any contacts
online to chat?
5 contacts are
available to chat
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AS CALLS PASS-THROUGH, IT CAN
PERFORM VALIDATION AND MUCH MORE
MORE THAN JUST PUBLISH/SUBSCRIBE
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MODULES
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MODULE PATTERN
OBJECT LITERALS
AMD
ASYNCHRONOUS MODULES - UNTIL WE GET ES HARMONY
SIMULATED PRIVACY
MODULAR OBJECTS
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LARGE APPLICATIONS
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WHAT IS A LARGE APP?
A NON-TRIVIAL APPLICATION REQUIRING SIGNIFICANT
DEVELOPER EFFORT TO MAINTAIN, WHERE MOST OF THE
HEAVY LIFTING OF DATA MANIPULATION AND DISPLAY
FALLS TO THE BROWSER
IT ISN’T ABOUT LOC!
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GWT->JAVASCRIPT, LOTS OF COMPONENTS
GMail
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MODULARIZED HOMEPAGE
Yahoo!
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BRAINSTORM
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LOOSELY COUPLED
ARCHITECTURE
SMALLER
INDEPENDENT
MODULES
FLEXIBILITY TO
CHANGE
WHAT ARE WE LOOKING FOR?
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NOTIFY US WHEN
SOMETHING
INTERESTING HAPPENS
DON’T TOUCH ANYTHING
THEY DON’T HAVE TO
CAN’T CAUSE THE
ENTIRE APP TO
STOP WORKING
MODULES:
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DEDICATE SUFFICIENT TIME TO PLANNING
THE ARCHITECTURE THE MAKES THE MOST
SENSE FOR YOUR APP - IT’S OFTEN
MORE COMPLEX THAN WE INITIALLY THINK.
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SOLUTION: COMBO!
+ +
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1. THE APPLICATION CORE
USING THE MEDIATOR PATTERN
MANAGES THE MODULE
LIFECYCLE: STARTS, STOPS,
RESTARTS IF NECESSARY
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CODE SAMPLE:
app.core = (function(){
var data = {};
return{
define: function( id, constructor ){
//... type checking not show
var c = constructor(app.facade.define(this,id));
//..further instance checks not shown
data[id] = { define: constructor, instance:null;
},
start: function( id ){
var module = data[id];
module.instance =module.define(app.facade.define(this, id));
module.instance.initialize();
},
stop: function( id ){
var module = data[id];
if(module.instance){
module.instance.destroy();
}
...
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1. THE APPLICATION CORE
USING THE MEDIATOR PATTERN
REACTS TO ACTIONS PASSED
BACK FROM A SANDBOX
(FACADE) - HANDLES LOGIC
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CODE SAMPLE:
// The sandbox has publish() and subscribe() methods
// which the mediator implements
// subscribe
register:function(events, module){
if(app.core.dom.isObject(events) && module){
if(data[module]){
data[module].events = events;
}
}
},
// publish
trigger: function(events){
if(app.core.dom.isObject(events)){
var mod;
for(mod in data){
if(data.hasOwnProperty(mod)){
mod = data[mod];
if(mod.events && mod.events[events.type]){
...
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1. THE APPLICATION CORE
USING THE MEDIATOR PATTERN
ENABLES ADDING AND
REMOVING MODULES
WITHOUT CAUSING BREAKS
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CODE SAMPLE:
// Summary definitions of a simple todo app
// Easy to add/remove/start/stop
app.core.define('#todo-counter', ...);
app.core.define('#todo-field',...);
app.core.define('#validate', ...);
app.core.define("#todo-list", ...);
app.core.define("#todo-entry", ...);
app.core.define('#error', ...);
app.core.define('#validate', ...);
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1. THE APPLICATION CORE
USING THE MEDIATOR PATTERN
HANDLES ERROR DETECTION
AND MANAGEMENT
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2. THE SANDBOX
USING THE FACADE PATTERN
AN ABSTRACTION OF THE
CORE THAT’S AN API FOR
COMMON TASKS, USED BY
MODULES
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CODE SAMPLE:
app.sandbox = {
define: function( el, module ){
return{
publish: function( eventType ){
app.events.trigger( eventType );
},
subscribe: function( eventType ){
app.events.register( eventType, module);
},
find: function( selector ){
return app.dom.query(el).find(selector);
},
ignore: function( eventType ){
app.events.remove( eventType, module);
}
}
}
};
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2. THE SANDBOX
USING THE FACADE PATTERN
INTERFACE FOR ENSURING
MODULES DON’T DIRECTLY
ACCESS THE CORE/LIBRARIES
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CODE SAMPLE:
// Note: all input validation done by the mediator
animate:function( props ){
return core.dom.animate(props);
},
bind:function( el , type, fn ){
dom.bind(el, type, fn);
},
unbind:function( el , type, fn ){
dom.unbind(el, type, fn);
},
ignore:function( e ){
events.remove(e, module);
},
createElement:function( el, config ){
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2. THE SANDBOX
USING THE FACADE PATTERN
PERMISSIONS MANAGER,
SECURING WHAT MODULES
CAN/CAN’T ACCESS
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CODE SAMPLE:
// A permissions structure can support checking
// against subscriptions prior to allowing them
// to clear. This enforces a flexible security
// layer for your application.
var permissions = {
newMessage: {
messageComposer:true,
notifications: true,
offlineStore: false
},
trashMessage:{
messageComposer: true,
notifications: false
},
...
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3. MODULES:
UNIQUE (INDEPENDENT)
BLOCKS OF FUNCTIONALITY
FOR YOUR APPLICATION
USING AMD/OBJECT LITERALS/MODULE PATTERN
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CODE SAMPLE (STATUS):
app.core.define('#status-widget', function( sandbox ){
var status = "none";
return{
initialize: function(){
var el = sandbox.find('.editor');
sandbox.subscribe({
'new-entry': this.updateStatus
});
},
destroy: function(){
status = "";
},
updateStatus: function(data){
status = "edited";
sandbox.find('.status').html(status);
sandbox.publish('status-updated');
}
}
});
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3. MODULES:
SUBSCRIBE TO
NOTIFICATIONS OF INTEREST,
RAPIDLY REACT TO CHANGES
USING AMD/OBJECT LITERALS/MODULE PATTERN
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CODE SAMPLE:
app.core.define('#status-widget', function( sandbox ){
var status = "none";
return{
initialize: function(){
var el = sandbox.find('.editor');
sandbox.subscribe({
'new-entry': this.updateStatus
});
},
destroy: function(){
status = "";
},
updateStatus: function(data){
status = "edited";
sandbox.find('.status').html(status);
sandbox.publish('status-updated');
}
}
});
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3. MODULES:
NOTIFY THE APP WHEN
SOMETHING INTERESTING
HAPPENS (PUBLISH)
USING AMD/OBJECT LITERALS/MODULE PATTERN
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CODE SAMPLE:
app.core.define('#status-widget', function( sandbox ){
var status = "none";
return{
initialize: function(){
var el = sandbox.find('.editor');
sandbox.subscribe({
'new-entry': this.updateStatus
});
},
destroy: function(){
status = "";
},
updateStatus: function(data){
..
sandbox.publish({
type : 'status-updated',
data : {value: ‘A new entry has been added’}
});
}
}
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DEMO TIME!
SEE: https://github.com/addyosmani/largescale-demo
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REVIEW
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A PATTERN FOR LARGE-SCALE APPS
CORE SANDBOX MODULES
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• Modules have fewer dependencies
• They can be managed so that the application
doesn’t (or shouldn’t) fall over.
• You can theoretically pick up any module, drop it
in a page and start using it in another project
AND ONE LAST REMINDER ABOUT ‘WHY?’
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FURTHER READING
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• Patterns For Large-scale JavaScript Application
Architecture http://addyosmani.com/largescalejavascript/
• Understanding The Publish/Subscribe Pattern http://
msdn.microsoft.com/en-us/scriptjunkie/hh201955.aspx
• Writing Modular JavaScript with AMD, CommonJS
& ES Harmony http://addyosmani.com/writing-modular-js
• Understanding MVC & MVP For JS Developers http://
bit.ly/wJRR59
MORE INFORMATION
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• Backbone Fundamentals (book): http://
backbonefundamentals.com
• Essential JavaScript Design Patterns (e-book) http://
bit.ly/bMyoQ9
• Building Large-Scale jQuery Applications http://
addyosmani.com/blog/large-scale-jquery/
FREE BOOKS/ARTICLES
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Blog
Twitter
GitHub
http://addyosmani.com
@addyosmani or @addy_osmani
http://github.com/addyosmani
THAT’S IT! FOR MORE FROM ME: