Javascript MVC & Backbone Tips & Tricks

MVC Frameworks
in Javascript
Hjörtur Hilmarsson
@hjortureh

Agenda

• Why MVC in Javascript ?
• Backbone & Spine
• Backbone fundamentals
• Backbone Tips & Tricks

“The world web
is changed”

Markup

<form>

! 
! <input id="name" name="name" type="text" placeholder="What is your name?" required />

! 
! <input id="email" name="email" type="email" placeholder="What is your email?" required />

! 
! <textarea id="message" name="message" placeholder="Hello!" required ></textarea>

! 
! <input id="submit" name="submit" type="submit" value="Send" />

! 
! <span id="message" ></span>

</form>

Javascript - Old style

$("form").submit(function( e ) {
! ! ! !
! e.preventDefault();

! // get values
var $form = $(this);
var data = {
name: $form.find("[name=name]").val(),
email: $form.find("[name=email]").val(),
message: $form.find("[name=message]").val()
};

// ajax request
$.ajax({
type: "post",
url: "/enquiry",
contentType: "application/json",
dataType: "json",
data: data,
success: function() {
$form.find("#message").text("Message posted").fadeIn();
},
error: function() {
$form.find("#message").text("Sorry, there was an error").fadeIn();
}
});
});

Controller - MVC style

$("form").submit(function( e ) {
! ! ! !
! e.preventDefault();

! // get values
! var $form = $(this);
! var data = {
! ! name: $form.find("[name=name]").val(),
! ! email: $form.find("[name=email]").val(),
! ! message: $form.find("[name=message]").val()
! };

! // model
! var enquiry = new Enquiry( data );
!
! enquiry.save(
! ! function() {
! ! ! $form.find("#message").text("Message posted");
! ! },
! ! function() {
! ! ! $form.find("#message").text("Sorry, there was an error");
! ! }
! );
});

Model - MVC style

// constructor
var Enquiry = function( data ) {
! this.data = data;
};

// save method
Enquiry.prototype.save = function( success, error ) {

! // ajax request
! $.ajax({
! ! type: "post",
! ! url: "/enquiry",
! ! contentType: "application/json",
! ! dataType: "json",
! ! data: this.data,
! ! success: success,
! ! error: error
! });

};

Backbone.js controller view
var ContactUs = Backbone.View.extend({
!
! // local variables
! el: $("form").get(0),
! events: { "submit": "submit" }
! model: new Enquiry,

! // constructor
! initialize: function() {
! ! this.model.bind("create", create, this );!
! ! this.model.bind("error", error, this );!
! },

! // submit event
! submit: function( e ) {
! ! e.preventDefault();
! !
! ! var data = {
! ! ! name: this.$("[name=name]").val(),
! ! ! email: this.$("[name=email]").val(),
! ! ! message: this.$("[name=message]").val()
! ! };

! ! this.model.save();
! },

! // success callback
! create: function() {
! ! this.$("#message").text("Message posted");
! },

! // error callback
! error: function() {
! ! this.$("#message").text("Sorry, there was an error");
! }

});

Backbone.js model

var Enquiry = Backbone.Model.extend({});

MVC Benefits

Structure
Classes, inheritance, common patterns.

Modular
Communication via events, lousily coupled & testable components.

Common services
Back and forward history, clients-side url resources, utilities.

Persistence layers
RESTful sync, local storage, web sockets and more.

Community
Patterns, mixins, conferences and more.

Challenges

• Going out of the box
• Nested models
• Complex ajax requests
• Understanding the limitations
• Its still hard

Challenges

TodoMVC - http://addyosmani.github.com/todomvc/

To mvc, or not to mvc ?

Use for one page apps

Use for complex client-side UIs & crud

Use not only for UI sugar

Use not for just rendering HTML

Use not for inflexible backends

• Created 2010 by Jeremy Ashkenas
• File size 5.4k
• Depends on Underscore.js ( 4k )
• Very popular

http://blog.fogcreek.com/the-trello-tech-stack/

https://engineering.linkedin.com/mobile/linkedin-ipad-using-local-storage-snappy-mobile-apps

Spine

• Inspired by Backbone
• Written in CoffeeScript by Alex McCaw
• File size 7k
• Introduced async UI concept

Text

http://hjortureh.tumblr.com/post/22117245794/spine-js-vs-backbone-js

Modules

• Events
• Models
• Collections
• Views
• Routes
• History

Events

• Consists of on, off & trigger methods
• All Backbone modules can trigger events
• All Javascript object can be extended with
the Backbone events module

Event example

Event triggered inside User class when name is changed

this.trigger("change:name", "Mr Hilmarsson");

Bind to a name change event

user.on("change:name", function( name ) {
! alert( "Name changed to " + name );
});

Models

• Wrapper for JSON & syncing via JSON
• RESTful by default. Overwrite sync
method to change persistence logic.
• Communicates via events ( create, change,
destroy, sync, error, add , remove )
• Can handle validation

Model

var Todo = Backbone.Model.extend({

defaults: {
done: false
},

toggle: function() {
this.save({done: !this.get("done")});
},

clear: function() {
this.destroy();
}

});

TodoMVC - example

http://addyosmani.github.com/todomvc/architecture-examples/backbone/index.html

Collections

• List of models
• Fires events for collection and the models
• Keeps models sorted
• Includes many utility methods

Collection

var TodoList = Backbone.Collection.extend({

model: Todo,

done: function() {
return this.filter(function(todo){ return todo.get('done'); });
},

remaining: function() {
return this.without.apply(this, this.done() );
},

comparator: function(todo) {
return todo.get('order');
}

});

Views

• Bridge the gap between the HTML and
models
• DOM element ( this.el ) represents the
context
• Uses jQuery / Zepto / ender for DOM
manipulation
• Listens for UI events & model events
• Use render method to create view

Organizing views

1:1
View Model

Todo view

var TodoView = Backbone.View.extend({

tagName: "li",

template: _.template($('#item-template').html()),

events: {
"click .check" : "toggleDone"
},

initialize: function() {
_.bindAll(this, 'render' );

this.model.bind('change', this.render );
},

render: function() {
$(this.el).html(this.template(this.model.toJSON()));
return this;
},

toggleDone: function() {
this.model.toggle();
}

...
}

Template

<script type="text/template" id="item-template">

<div class="todo <%= done ? 'done' : '' %>">
<div class="display">
<input class="check" type="checkbox" <%= done ? 'checked="checked"' : '' %> />
<label class="todo-content"><%= content %></label>
<span class="todo-destroy"></span>
</div>
<div class="edit">
<input class="todo-input" type="text" value="<%= content %>" />
</div>
</div>

</script>

App view

var AppView = Backbone.View.extend({

! el: $("#todoapp"),

! ! initialize: function() {
! ! _.bindAll(this, 'addOne', 'addAll', 'render' );

! ! Todos.on('add', this.addOne);
! ! Todos.on('reset', this.addAll);

! ! Todos.fetch();
! },

! addOne: function(todo) {
! ! var view = new TodoView({model: todo});
! ! this.$("#todo-list").append(view.render().el);
! },

! addAll: function() {
! ! Todos.each(this.addOne);
! }

! ...

}

Router & History

• Provides a way to map URL resources
• Enables client-side back & forward
navigation
• Use Hash-change by default. Supports
push state ( History API )

Be Careful!

• Its stateful !
• Its not easy
• Don’t set navigate trigger to true

Router

APP.Router = Backbone.Router.extend({

routes: {
"new": "newNote",
":id": "editNote",
"": "home"
},

home: function() {
APP.appView.home();
},

newNote: function() {
APP.appView.newNote();
},

editNote: function( id ) {
APP.appView.editNote( id );
}

});

History - example

Start listening for hash-change events

// Start the history
Backbone.history.start();

Use html5 history API

// Start the history
Backbone.history.start({pushState: true});

Tips & Tricks
• Tip #1 - Bootstrapping data
• Tip #2 - Async user interfaces
• Tip #3 - Nested models
• Tip #4 - Custom ajax requests
• Tip #5 - Zombies to heaven
• Tip #6 - The toolbox
• Tip #7 - Test, test, test
• Tip #8 - CoffeeScript
• Tip #9 - Remember the basics
• Tip #10 - Bonus points

Bootstrapping data

• Using fetch extends waiting time
• Possible to bootstrap the most important
data when the page is rendered
• No loading spinners !

Bootstrapping Data

The code

// Current user
APP.currentUser = new APP.Models.User(<%= @current_user.to_json.html_safe %>);

// Notes
APP.notes.reset(<%= @notes.to_json.html_safe %>);

After render
// Current user
APP.currentUser = new APP.Models.User({
id: 1, username: "hjortureh",
name: "Hjortur Hilmarsson",
avatar: "avatar.gif"
});

// Notes
APP.notes.reset([
{ id: 1, text: "Note 1" },
{ id: 1, text: "Note 2" },
{ id: 1, text: "Note 3" }
]);

Importance of speed
Amazon
100 ms of extra load time caused a 1% drop in
sales (source: Greg Linden, Amazon).

Google
500 ms of extra load time caused 20% fewer
searches (source: Marrissa Mayer, Google).

Yahoo!
400 ms of extra load time caused a 5–9%
increase in the number of people who clicked
“back” before the page even loaded (source:
Nicole Sullivan, Yahoo!).

37 Signals - Basecamp
500 ms increase in speed on basecamp.com
resulted in 5% improvement in conversion rate.

Async user interfaces

• Models are optimistic by default
• UI is updated before server response
• Use cid as a unique identifier on the client
• No loading spinners !

Question

Has many

Answers

Nested models

• Nested models are common
• No official way of doing it
• Overwrite parse after ajax request

• Overwrite toJSON before ajax request

• Backbone-relational mixin could help

Nested models
var Question = Backbone.Model.extend({

initialize: function() {

// collection instance
this.answers = new Answers;

},

parse: function(resp, xhr) {

// fill nested model
if( _.isArray( resp.answers ) ) {
this.answers.reset( resp.answers );
}

return resp;

},

toJSON: function() {

// send nested models
return $.extend(
this.attributes(), {
answers: this.answers.toJSON()
}
);
}

});

Custom ajax request

• Sometimes RESTful methods are not
enough
• Example: Sorting tasks in to-do list

Sorting - Custom request

saveOrder: function() {
!
! var ids = this.pluck("id");
!
! window.$.ajax({
! ! url: "/tasks/reorder",
! ! data: {
! ! ! ids: ids
! ! },
! ! type: "POST",
! ! dataType: "json",
! ! complete: function() {
! ! ! // Handle response
! ! }
! });
!
}

Zombies to heaven

• Its not enough to remove views from the
DOM
• Events must be released so you don’t have
zombies walking around

Zombies to heaven

// same as this.$el.remove();
this.remove();

// remove all models bindings
// made by this view
this.model.off( null, null, this );

// unbind events that are
// set on this view
this.off();

Use the toolbox

• Underscore has some wonderful methods
• isFunction, isObject, isString, isNumber,
isDate & more.
• Underscore: http://
documentcloud.github.com/underscore

Underscore
Line 865 from the Backbone.js code.

// Underscore methods that we want to implement on the Collection.
var methods = ['forEach', 'each', 'map', 'reduce', 'reduceRight', 'find',
'detect', 'filter', 'select', 'reject', 'every', 'all', 'some', 'any',
'include', 'contains', 'invoke', 'max', 'min', 'sortBy', 'sortedIndex',
'toArray', 'size', 'first', 'initial', 'rest', 'last', 'without', 'indexOf',
'shuffle', 'lastIndexOf', 'isEmpty', 'groupBy'];

// Mix in each Underscore method as a proxy to `Collection#models`.
_.each(methods, function(method) {
Collection.prototype[method] = function() {
return _[method].apply(_, [this.models].concat(_.toArray(arguments)));
};
});

Testing

• Recommend Jasmine for testing

• Recommend Sinon to fake the server

• jQuery-jasmine to test views

• Use setDomLibrary method to fake jQuery

Jasmine with fake server & spy
it('Should sync correctly', function () {

// mockup data
var note = new APP.Models.Note({ text: "Buy some eggs" });

// fake server
this.server = sinon.fakeServer.create();

// fake response
this.server.respondWith( "POST", "/notes",
[ 200,
{"Content-Type": "application/json"},
'{ "id": 1, "text": "Remember the milk" }' ]
);

// spy on sync event
var spy = sinon.spy();
note.on("sync", spy );

// save model
note.save();

// server repsonse
this.server.respond();

// assert
expect( spy ).toHaveBeenCalledOnce();
expect( spy ).toHaveBeenCalledWith( note );
expect( note.get("text") ).toEqual( "Remember the milk" );

// restore fake server
this.server.restore();

});

CoffeeScript

• Advanced programing language
• Compiles to javascript
• Same creator of Backbone and
CoffeeScript
• Integrates well with Backbone

Coffee Script example
Extending Backbone module

class TodoList extends Backbone.View

Double arrow to bind to the context
Use @ instead of this
Last line is the return value, returns this

_.bindAll( this, 'render' )

render: =>
@$el.html( @template( @.model.toJSON() ))
@

Need to call super on parent constructors

initialize: ->
! super

The basics

• The basics still apply with MVC in place
• Minimize ajax requests
• Keep your views thin & models fat
• Understanding Javascript is the key

Bonus points

• Read the documentation
• Read the source code
• Just do it !

Tack så mycket
Hjörtur Elvar Hilmarsson
@hjortureh

Javascript MVC & Backbone Tips & Tricks

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