Planbox Backbone MVC

Migrating MVC to the
Front-end using
Backbone JS
Martin Drapeau
CTO & Co-founder Planbox
Feb 2012

Martin Drapeau Feb 2012

AGILE PROJECT MANAGEMENT

Based on
SCRUM



Cloud SAAS
trying to solve
a big
problem...


Source: www.solutionsiq.com


DEMO TIME!



Built on LAMP



We use
popular
frameworks



Single Page
Application

Very dynamic



Client http://www.planbox.com/plan

Web Page
HTML
CSS

Was architected 1 Javascript

on Back-end Server 4
5

Controller View

MVC 2
Model

3

Database

Engine


The Problem


MVC in the Back-end
HTML • HTML generated in PHP
HTML
HTML • AJAX to update page
fragments
• Javascript is the duck-tape
HTML

Feature development
Bottleneck!


MVC in the Back-end
A

B

C

Change of A requires update of B and C.
Why does the back-end have to do that?


MVC in the Back-end
does not scale for
Dynamic Web Apps
WHY?
• Where do I write that code? PHP or JS?
• Can we push to production? No, back-end has
changed!
• Developers must be trained on PHP and JS.
• Etc...


The Solution


Move MVC to Front-end

Let’s write our code in Javascript!


Ground Rules
Back-end
• Becomes a REST API. Talks JSON.
Front-end
• Handles UI interactions.
• Replicates data models.
• Replicates business logic only when necessary.
Must be fast and lightweight!


Choose a Framework

Requirements:
• Lightweight - fast to load & mobile friendly
• Extendible
• jQuery Friendly
• Open Source
• Can be integrated gradually


Contenders (back in Nov 2010)
• SproutCore
A widget framework, too big and constraining!

• Javascript MVC
Too much stuff in there! Constraining and awkward.

• Knockout
MVVM?? I don’t want to couple views and models!

• Backbone JS
Small, has collections, HTML templates, etc. Natural fit.

A recent source of comparisons can be found here:
http://codebrief.com/2012/01/the-top-10-javascript-mvc-frameworks-reviewed/


Backbone JS


Backbone.js gives structure to web applications
by providing models with key-value binding and
custom events, collections with a rich API of
enumerable functions, views with declarative
event handling, and connects it all to your
Jeremy Ashkenas,
existing API over a RESTful JSON interface. Author of
Backbone JS ,
Underscore JS, and
CoffeeScript
•Open Source
•5.3kb, Packed and gzipped
•87 contributors
•6,500 watchers

Backbone’s Take on MVC
• Data and presentation are decoupled:
– “stop tying your data to the DOM”

• Models use the Pub/Sub pattern:
– Views subscribe to model change events to re-render

• Collections are used to group models:
– Events bubble up to collections. Subscribe to the add event on the collection
to get notified.

• Models are synchronized with your back-end:
– Via AJAX to your RESTful API. CRUD by default.

• Views control user interactions and trigger model updates:
– HTML templates, jQuery or Zepto DOM manipulation and AJAX

Where is the C in MVC? The Controller is in the View.

Model – attributes and events
var story = new Backbone.Model({
id:1,
name:"As a coder I want MVC in the front-end",
points:21
});

story.bind("change:points", function(model, points) {
console.log("Story #"+model.id+" points changed from "+
model.previous("points")+" to "+points);
});

story.get("points"); // Returns 21

story.set({points:99});

Console
>>> Story #1 points changed from 21 to 99


Collection – model IDs and Underscore JS
var stories = new Backbone.Collection([{
id:1,
name:"As a coder I want MVC in the front-end",
points:21
}, {
id:2,
name:"As I PM, I want visibility",
points:33
}]);

var story = stories.get(2); // Return model #2

stories.pluck('points'); // Returns [21, 33]


Collection – event bubbling
stories.bind("add", function(collection, model) {
console.log("Story #"+model.id+" added to collection");
});

stories.add({
id:3,
name:"As a driver, I want a reliable car"
points:5
});

stories.pluck('points'); // Returns [21, 33, 5]

Console
>>> Story #3 added to collection


Collection – ordered or unordered

stories.comparator = function(modelA, modelB) {
var a = modelA.get('points');
var b = modelB.get('points');
return a < b ? -1 : a > b ? 1 : 0;
}

stories.sort();



Collection – fetch from server with AJAX
stories.url = "/api/get_stories"; // REST API

// Preprocess JSON before creating models
stories.parse = function(object) {
if (object && object.content) return object.content;
};

stories.fetch({
data: {product_id:1}, // jQuery $.ajax arguments
dataType: 'JSONP',
success: function(collection) {
console.log('Loaded '+collection.length+' stories');
},
error: function(collection, error) {
console.log(error);
}
});

>>> Loaded 87 stories Console


View – Render a model
Use of extend to create a new Class.
StoryView = Backbone.View.extend({
className: "story",
render: function() {
var view = this;
var model = this.model;
$(this.el).text(model.get('name'));
return view; // Always return view for chaining
}
});

var view = new StoryView({model: story});
view.render();
$(view.el).appendTo('body');


View – HTML template (Underscore JS)
<script type="text/template" id="story_template">
<label>#<%=id%></label>
<input type="text" value="<%=name%>" />
<button>Delete</button>
</script>

StoryView = Backbone.View.extend({
className: "story",
template: _.template($("#story_template").html()),
render: function() {
var view = this;
$(this.el).html(view.template(model.toJSON()));
return view;
}
});


View – User interaction
initialize: function() {
var view = this, model = view.model;
model.bind("change", view.render, view);
model.bind("remove", view.remove, view);
return view;
},
events: { // Delegate events
"change input": "saveName",
"click button": "del"
},
saveName: function() {
var new_name = $(view.el).children("input").val();
model.save({name:new_name}); // Call server then model.set
return view;
},
del: function() {
model.destroy(); // Call server then collection remove
return view;
}


Client/Server Sync Loop

1. Push changes to server
2. Receive acknowledgement
3. Set attribute change on data model
4. View captures change event
5. View renders (maybe)

Event Payload – options argument
The options argument can be used as an event payload.
Use it not to render unnecessarily.

saveName: function() {
var new_name = $(view.el).children("input").val();
model.save({name:new_name}, {caller:view});
return view;
}
render: function(options) {
options || (options = {});
if (options.caller == this) return this;

var view = this;
$(this.el).html(view.template(model.toJSON()));
return view;
}


View – Render a collection
StoriesView = Backbone.View.extend({
tagName: "ul",
className: "stories",
initialize: function() {
var view = this;
var collection = view.collection;
collection.bind('add', view.addOne, view);
collection.bind('reset', view.addAll, view);
},
addOne: function(model) {
var view = this;
var story_view = new StoryView({model: model});
story_view.render();
$(view.el).append(story_view.el);
return view;
},
addAll: function() {
var view = this, collection = view.collection;
collection.each(function(model) {
view.addOne(model);
});
return view;
}
});


Other Backbone Artefacts
• Sync
– Handles client/server communication
– Uses jQuery (or Zepto) $.ajax
– Follows CRUD (Model.url and Collection.url)

• Router & History
– Handle URL changes and that Back button
– Wraps HTML5 History API
– Graceful polling fallback


Backbone JS
got
Planboxed


No CRUD - Rich verbs mapping to API
• A story model has:
– save  www.planbox.com/api/update_story
– move  www.planbox.com/api/move_story
– duplicate  www.planbox.com/api/duplicate_story
– etc...

• Did not use Sync
– Overwrote methods fetch, save, etc.
– Used jQuery $.ajax of course


Local Persistence in URL
• State of page is saved in URL’s hash tag using
JSON (quotes are stripped)

Opened tab in Story
Selected Story
Pane

http://planbox.com/nik#{product_id:1,story_pane_tab:tasks,filter_id:1,story_id:199486}

Top level project
selected Selected Sprint

https://github.com/martindrapeau/JSON-in-URL-Hash


Model Selection
NikModel = Backbone.Model.extend({
selected: false,
select: function(options) {
if (this.selected) return this;
this.selected = true;
if (!options.silent)
this.trigger('select', this, options);
return this;
},
unselect: function(options) {
if (!this.selected) return this;
this.selected = false;
if (!options.silent)
this.trigger('unselect', this, options);
return this;
}


Selection in Collection
NikCollection = Backbone.Collection.extend({
model: NikModel,
select: function(model, options) {
var collection = this;
_.each(collection.selected(), function(model) {
model.unselect(options);
});
model.select(options);
return this;
},
selected: function() {
return _.select(this.models, function(model) {
return model.selected;
});
},


Collection Filtering
// Argument filters is a hash of attributes and their
// allowed values. For example: filters.type = ['bug']

// Property Model.filtered is a hash of failed conditions.
// For example is Model.type = 'feature', then
// Model.filtered = ['bug'].

Model.filter(filters, options)
Model.filtered // Array of filtered out attributes

Collection.filter() // Runs filtering on the collection
Collection.filtered()
Collection.not_filtered()


Sort DOM Against Collection
DOM Collection
#199834
#190293
#201293
#150932
#188456
#178545
#190293

• Stories are ordered by priority (same for everyone)
• Need to sync order of stories (i.e. after drag and drop)
• Helper function to re-order DOM elements minimizing DOM
manipulations


Cascading Events – Model bound to Collection

• Summary Model listens to changes on Stories Collection
• Keeps sums of points, resources, estimate-hours, etc...
• Views tied to it update in real time!


Custom Widgets
• All widgets are custom
– Ligthweight and flexible
– Fast to load
– No jQuery UI with large CSS and JS footprint
– Use of Backbone Models and Collections

• Types of widgets
– Dialogs
– Drop-downs
– Date picker
– Auto-complete
– Input


Backbone Auto-complete Widget
var collection = new Backbone.Collection([
{id:"AB", name:"Alberta"},
{id:"BC", name:"British Columbia"},
{id:"MB", name:"Manitoba"},
// ...
{id:"AP", name:"Armed Forces Pacific"}
]);

$('#states_provinces').autocomplete({
collection: collection,
attr: 'name',
noCase: true,
ul_class: 'autocomplete shadow',
ul_css: {'z-index':1234}
});

http://www.planbox.com/blog/news/updates/jquery-autocomplete-plugin-for-backbone-js.html


Real Time – No page reload
• Polling server at 15 second interval
(Tried COMET but was overkill)

• Change history Collection
– Last transaction ID is kept in client
– Every 15 seconds, ask server for newer updates
– Server sends updated Models


Deployment
Build procedure
– Javascript files are minified and collated
– Version is automatically incremented
– ?v=3.1234 is added to all CSS/JS files (prevent caching issues)

Planbox - Minifying Javascript Files...
Version: 3.019

3rd.js 70397 bytes hom.js 9758 bytes
jwysiwyg/jquery.wysiwyg.min.js 36278 bytes acc.js 14505 bytes
zeroclipboard/zeroclipboard.min.js 6747 bytes rep.js 84129 bytes
adw.js 32136 bytes table.js 42311 bytes
common.js 195872 bytes mobile_3rd.js 74594 bytes
nik.js 230008 bytes mobile_common.js 71371 bytes
mag.js 53275 bytes mobile.js 116873 bytes


The Result


3rd Party Libraries Application Load Size
JS fileGzipped Size (KB) Content (KB)
jquery.min.js 29.34 83.26
jquery.wysiwyg.min.js 10.54 35.43
zeroclipboard.min.js 2.56 6.59
3rd.js 17.82 68.75
60.26 194.03

common.js 41.27 191.28
Application

nik.js 45.58 224.62
86.85 415.9

Total 147.11 609.93

346 Story Models (JSON) 124.67 949.01
KB/Story 0.36 2.74


Benefits of MVC in front-end
• Decouple back-end and front-end
– The API becomes the back-end contract (and
performance too I hope).
– Back-end and front-end teams are decoupled

• Bandwidth reduction
– Data and presentation loaded once
– Subsequently, only Model deltas are transferred

• Reduce server load
– All UX processing is performed client side


Benefits of MVC in front-end
• Release anytime
– Majority of code changes are in UI
– Changes happen faster in front-end than back-end
– Concurrent versions of the client can exist. Hit F5 to get the
latest and greatest.
– Back-end doesn’t change – no risk of conflicts in browser

• Faster development
– Know and master one language
– Use the browser as your development and testing bed (yeah
Firebug!)
– Release often
– Don’t accumulate ‘corrected’ defects in development – push
them out as they are fixed


Acknowledgements

Mathieu Dumais-Savard
Sébastien Giroux
Jeremy Ashkenas
js-montreal.org


References & Links
Javascript Frameworks
• Backbone JS http://documentcloud.github.com/backbone/
• JavascriptMVC http://javascriptmvc.com/
• SproutCore http://sproutcore.com/
• Underscore JS http://documentcloud.github.com/underscore/
• jQuery http://jquery.com/

Helpers
• John Resig’s Javascript Micro-Template http://ejohn.org/blog/javascript-micro-templating/
• JSON2 http://www.json.org/js.html
• jsmin (PHP minifier) https://github.com/rgrove/jsmin-php/

Books
• JavasScript Web Applications (Alex MaxCaw) http://shop.oreilly.com/product/0636920018421.do
• jQuery Cookbook (Cody Lindley) http://shop.oreilly.com/product/9780596159788.do?sortby=bestSellers

Planbox Open Source Contributions
• Backbone Widgets https://github.com/martindrapeau/Backbone-Widgets
• JSON in URL Hash https://github.com/martindrapeau/JSON-in-URL-Hash


Questions?


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