9 Tips for a clean BackboneJS App

http://rvl.io/adamterlson/

@adamterlson

Current: JS dev at Best Buy

Former: JS dev at Thomson Reuters

JS <3

Why this presentation?

Working with large teams
Developers unfamiliar with JavaScript
Developers unfamiliar with Backbone
Migrated legacy app into new "SPA"
No unit tests

"Opportunities"

#1 : Organization Inside & Out

Outside is Obvious

Backbone Boilerplate:

.
├── app
│   ├── app.js
│   ├── config.js
│   ├── main.js
│   ├── router.js
│   └── styles
│   |   └── index.css
├── vendor
│   ├── h5bp
│   │   └── css
│   │   |   ├── main.css
│   │   |   └── normalize.css
│   └── jam
│   |   ├── backbone
│   |   ├── backbone.layoutmanager
│   |   ├── jquery
│   |   ├── lodash
│   |   ├── underscore
│   |   ├── require.config.js
│   |   └── require.js
│   └── js
│   |   ├── libs
│   |   │   ├── almond.js
│   |   │   └── require.js
├── favicon.ico
├── grunt.js
├── package.json
├── index.html
└── test
    ├── jasmine
    └── qunit

No one answer to file structure -- Consistency is most important

What about Inside?

All sections need not apply.


var myExampleView = Backbone.View.extend({
    // Properties
        
    // Backbone
        
    // Bootstrap
        
    // Rendering
        
    // Backbone Events
        
    // UI Events
        
    // Methods
});

Nothing is stopping this:


myBusinessLogic: function () {
    if (this.myCollection.length && this.someValue) { // Where did these come from?!
        // ...
    }
},

//... 50 lines later

anotherFunction: function () {
    this.someValue = 10;
    this.myCollection = new Backbone.Collection();  // Oh, there it is!
},

// Properties

Self-documentation
Default values
Exclude native backbone objects/overrides

el
model
collection
options
id
className
tagName
attributes

// Properties


var myExampleView = Backbone.View.extend({
    // Properties
    
    pageSize: 10,
    activePage: 0,
    pages: null,
    
    additionalCollection: null,
    additionalModel: null
});

Warning: Use {} and [] wisely.

// Backbone

Backbone native, type-specific overrides

Model: urlRoot/url, idAttribute, defaults (make this a function by the way), initialize, save/fetch/sync/destroy/etc...
Collection: model, urlRoot/url, initialize...
View: template (though this isn't technically an override), events, initialize, id, className, tagName...

Display logic when appropriate

// Backbone (View)

// Backbone

template: _.template(exampleTemplate),

initialize: function () { },

events: {
    'mouseenter': 'onViewMouseEnter', // This binds to $el directly
    'submit form': 'onFormSubmit',
    'click .switch': 'onSwitchClick',
    'change input[name=property]': 'onPropertyInputChange'
}

//Backbone (Model)

// Backbone

urlRoot: '/api/exmaple',
idAttribute: 'ExampleId',

defaults: function () {
    return {
        foo: '',
        bar: { baz: 'baz' },
        listofstuff: []
    };
},

initialize: function () {  }

// Bootstrap

// Rendering

It's okay to have more than one!
One of two locations for touching the DOM in your view
Use .toJSON() when passing data to templates
Data should be pre-formatted wherever possible

Check out DustJS

// Rendering

// Rendering

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

renderSpotA: function () {
    this.$('#SpotA').html(...);
},

renderSpotB: function () {
    this.$('#SpotB').html(...);
}

//Backbone Events

Named: on<Object><Event>
Never executed directly
No presentation logic

// Backbone Events

onModelSync: function () {
    this.somePresentationLogic();
    this.someMorePresentationLogic();
}

//UI Events

The other acceptable location outside of render for touching the DOM
Same rules apply as Backbone events

// UI Events

onItemDeleteClick: function (e) {
    e.preventDefault();
    var itemId = $(e.target).data('itemId');
    this.deleteItemById(itemId);
}

// Methods

... they're functions

#2 : Consider "Bootstrap"

Goal

Find a place to do initial model hydration prior to first render.

Common (Bad) Solutions

Initialize gets executed by every unit test

Render is executed later to refresh the UI when the state changes.

Solution

Split initialize from 'pre-render' startup
Make the parent execute it

Initialize

For initializing values, setting options, and backbone event binding only (do not call render or make server calls)


initialize: function (options) {
    this.pageSize = options.pageSize || this.pageSize;
    this.additionalCollection = new Backbone.Collection();
       
    this.listenTo(this.model, 'sync', this.onModelSync)
        .listenTo(this.model, 'destroy', this.onModelDestroy)
        .listenTo(this.additionalCollection, 'add', this.onAdditionalCollectionAdd);
}

I don't like this.options--It's not explicit.

Bootstrap

Executed by the consumer to "kick off" your view
Server and rendering calls only
Orchestrator of when initial rendering happens

// Bootstrap - Hydration with spinner
bootstrap: function () {
    this.renderFrame(); //shows spinner(s)
    
    this.primaryModel.fetch().then(this.renderPrimary); 
    this.secondaryModel.fetch().then(this.renderSecondary);
    
    return this;
}

// Bootstrap - Hydration before any render
bootstrap: function () {
    $.when(
        this.primaryModel.fetch(),
        this.secondaryModel.fetch()
    ).then(_.bind(this.render, this));
    
    return this;
}

// Bootstrap - No hydration
bootstrap: function () {
    return this.render();
}

Usage

App

var myView = new MyView({ el: $spot });
myView.bootstrap();

// or, if you return `this`
var myView = new MyView({ el: $spot }).bootstrap();

Test

test("...", function() {
    // Arrange
    var myView = new MyView(); // Calls initialize

    // Act
    var result = myView.functionToTest();

    // Assert
    strictEqual(result, 1);
});

Benefits

Initialize free of AJAX calls/rendering
Fewer mocks leads to cleaner unit tests
Bootstrap after view creation

#3 : Write Backbone, not jQuery

Why not jQuery?

// Do not do this
presentationLogicAndClickEvent: function (e) {
    // ...
    
    this.model.set({ foo: this.$('#foo').val() }); // Mock val?!
    
    // ...
}

Unit Testing becomes a nightmare

Why not jQuery?

// Do not do this
presentationLogicAndClickEvent: function (e) {
    // ...
    
    this.$('#foo').val('new value');
    
    // ...
    
    this.render(); // Bye bye
}

DOM changes are temporary with render() around

Render is your friend

initialize: function () {
    this.listenTo(this.model, 'change', this.onModelChange);
},
onModelChange: function () {
    this.render();
},//...
presentationLogic: function (value) {
    this.model.set({ foo: value }); // trigger change, calls render
}

Silence (Delay < 0.9.10) events with { silent: true }

...Most of the time

Over reliance on render *can* impact performance.

Consider targeted rendering or subviews.

jQuery: Render, UI Events

Backbone: Everywhere else

#4 : Avoid Unnecessary Subviews

Signs to Separate

Segment independently operates upon its own model
Segment can live on its own in a different context
Your view is huge

One way to subview

// Backbone

template: _.template(frameTemplate),

// Rendering

render: function () {
    this.$el.html(this.template());
    this.renderItemList();
},

renderItemList: function () {
    var $ul = $('<ul/>');
    this.itemsCollection.each(function (item) {
        var itemView = new ItemView({ tagName: 'li', model: item }).bootstrap();
        $ul.append(itemView.$el);
    });

    this.$('#itemList').html($ul);
}

Construct subviews in render or initialize

Multi Template/Render

// Backbone

templates: {
    frame: _.template(frameTemplate),
    order: _.template(orderTemplate),
    user: _.template(userTemplate)
},

initialize: function () {
    this.orderModel = new orderModel();
    this.userModel = new userModel();
    
    this.listenTo(this.orderModel, 'change', this.onOrderModelChange); 
    this.listenTo(this.userModel, 'change', this.onUserModelChange); 
},

// Bootstrap

bootstrap: function () {
    $.when(
        this.orderModel.fetch(), 
        this.userModel.fetch()
    ).then(this.render);
    return this;
},

// Rendering

render: function () {
    this.$el.html(this.templates.frame());
    this.renderOrder();
    this.renderUser();
    return this;
},

renderOrder: function () {
    this.$('#order').html(this.templates.order({ 
        order: this.orderModel.toJSON() 
    }));
},

renderUserInformation: function () {
    this.$('#user').html(this.templates.user({ 
        user: this.userModel.toJSON() 
    }));
}

// Backbone Events

onOrderModelChange: function () {
    this.renderOrder();
},

onUserModelChange: function () {
    this.renderUser();
}

#5 : Unidirectional Knowledge

Hierarchy

router
├── view 1
│   ├── template
│   └── model
└── view 2
    ├── template
    ├── collection
    │   └── model
    └── first child view
        ├── template
        ├── model
        └── second child view
            └── template

Shared models make great "messengers"

Cross-sibling communication via global events

Via Promises (option 1)

Return a promise from a function (e.g. bootstrap)

// In parent view
renderModalForm: function () {
    var modalForm = new ModalFormView();
    modalForm.bootstrap().then(this.onModalFormDone);
},

// In child view
_dfd: null,
bootstrap: function () {
    this._dfd = $.Deferred();
    this.render();
    return this._dfd.promise();
},
something: function () {
    this._dfd.resolve(someObj);
}

Via Promises (option 2)

Make your view itself implement the promise API

_dfd: null,

constructor: function () {
    this._dfd = $.Deferred();
    this._dfd.promise(this); // Make this view a promise!
    this.always(_.bind(this.remove, this)); // Cleanup
    
    Backbone.View.prototype.constructor.apply(this, arguments);
}

something: function () {
    this._dfd.resolve();
}

Via Events

// In parent view
renderModalForm: function () {
    var modalForm = new ModalFormView({ model: this.model });
    this.listenTo(modalForm, 'saved', this.onModalFormSaved);
    modalForm.bootstrap();
},

// In child view
something: function () {
    this.trigger('saved', this.model);
}

#6 : Views Know `el`, Not The Live DOM

What's in the DIV?

var MyView = Backbone.View.extend({
    template: _.template('<div id="foo">initial text</div>'),
    
    initialize: function () {
        this.render();
    },
    
    render: function () {
        this.$el.html(this.template());
        $('#foo').html('changed text');
    }
});


var instance = new MyView();
$('#somespot').append(instance.$el);

Three steps to isolate your view from its context

Step 1: All selectors should be prefaced with `this`

this.$() ==> this.$el.find()

Timing

this.$() will always work (assuming it exists within $el)

$() will only work after $el is appended to the DOM

Context

this.$() also prevents views from hijacking other parts of the page

Step 2: View's Creator decides placement

Good options

Option 1:


    var instance = new MyView({ el: this.$('#MyViewSpot') }).render();

Warning: Giving an el which is already attached will paint immediately.

Warning: remove() will remove el, which isn't always desired.

Option 2:


    var instance = new MyView().render();
    this.$('#MyViewSpot').html(instance.$el);

Bad options

var view = Backbone.View.extend({ 
    el: $('#MyViewSpot')
});

Views shouldn't know about the DOM, remember?

var view = new Backbone.View();
view.setElement($someElement);

This is ~50% slower.

But setElement is useful outside of initial construction.

Step 3: Use delegated eventing

Backbone events are delegated for you

var view = Backbone.View.extend({ 
    events: {
        'mouseenter': 'onViewMouseEnter', // bound directly on $el
        'click #foo': 'onFooClick', // delegated on $el
        'submit form': 'onFormSubmit', // delegated on $el
        'scroll .some-div': 'onSomeDivScroll' // will fail, scroll doesn't bubble
    }
});

Eventually executes (in Backbone source):

if (selector === '') {
  this.$el.on(eventName, method);
} else {
  this.$el.on(eventName, selector, method);
}

What's in the DIV?

var MyView = Backbone.View.extend({
    template: _.template('<div id="foo">initial text</div>'),
    
    initialize: function () {
        this.render();
    },
    
    render: function () {
        this.$el.html(this.template());
        $('#foo').html('changed text');
    }
});

var instance = new MyView();
$('#somespot').append(instance.$el);

'initial text'

use this.$('#foo')

#7 : Don't cram everything in your view

View

Presentation/templating
UI Events
Model/Collection creation/orchestration
Model/Collection event binding
Application eventing
Presentation logic

Models should only know about data!

Collections know about models.

Model/Collection

Validation
Sync (and derivative) overrides
Sever-side data consumption
Nested models or collections
Parse/data manipulation
Utility methods
Event bindings/Custom events

No concept of UI or views!

Router

Routes
Loading appropriate view(s)
URLs

"It's too hard to unit

test JS code"

"Opportunities"

#8 : Arrange, Act, Assert

One Test to Rule Them All


test('...', function () {
   expect(100000000000000);
   var foo = bar;
   equal(foo.myFunctionToTest(), 'somevalue');
   
   foo.someLogic();
   equal(foo.property, 'newvalue');
   
   var baz = foo.createBaz();
   ok(baz.property);
   
   // and on and on and on...
});

Split tests up into three distinct parts

Arrange: Construction, setting, fake objects, stub methods
Act: Execute the method you are testing
Assert: Assertions

test('...', function () {
    // Arrange
    // Object creation
    
    // Act
    // Execute method being tested
    
    // Assert
    // *All* of your assertions
});

If you cannot fit your test into these parts in this order, write a second test.

In action (basic)


test('...', function () {
    // Arrange
    var foo = new bar();
    
    // Act
    var result = foo.someLogic();
    
    // Assert
    strictEqual(result, 'some value');
});

#9 : Write small unit tests

Unit testing with jQuery sucks


test('...', function () {
    var page = $('<div><a href="#"></a></div>');
    var model = new MyModel({ id: 10 });
    var view = new MyView({ el: page, model: model });
    page.find('a').click();
    ok(view.model.get('disabled'));
    model.set('something', false);
    equal(view.foo, 'bar');
    //etc
});

If you've followed my advice, this

will be entirely unnecessary.

Isolate your unit with mocks

Use SinonJS or another mocking library.

QUnit & Sinon Test Example

var MyView = Backbone.View.extend({
    initialize: function () { },
    render: function () { },
    someFunction: function () { 
        return this.model.fetch().done(this.render);
    }
});

module("...", {
    setup: function () {
        this.sandbox = sinon.sandbox.create();
    },
    teardown: function () {
        this.sandbox.restore();
    }
});

test("Positive Test", function() {
    // Arrange
    var dfd = $.Deferred();
    var promise = dfd.promise();
    
    var model = new Backbone.Model();
    var instance = new MyView({ model: model });
    this.sandbox.stub(instance, 'render');
    this.sandbox.stub(model, 'fetch').returns(promise);
    
    dfd.resolve();
    
    // Act
    var result = instance.someFunction();
    
    // Assert
    strictEqual(result, promise);
    ok(instance.render.called);
});

test("Negative Test", function() {
    // Arrange
    var dfd = $.Deferred();
    var promise = dfd.promise();
    
    var model = new Backbone.Model();
    var instance = new MyView({ model: model });
    this.sandbox.stub(instance, 'render');
    this.sandbox.stub(model, 'fetch').returns(promise);
    
    dfd.reject();
    
    // Act
    var result = instance.someFunction();
    
    // Assert
    strictEqual(result, promise);
    ok(!instance.render.called);
});

QUnit & Sinon Test Example: Initialize

var MyView = Backbone.View.extend({
    initialize: function (options) {
        this.foo = options.foo;
        this.additionalCollection = new Backbone.Collection();
  
        this.model.on('sync', this.onModelSync);
        
        this.someFunction();
    },
    someFunction: function () { },
    onModelSync: function () { }
});

module("...", {
    setup: function () {
        this.sandbox = sinon.sandbox.create();
    },
    teardown: function () {
        this.sandbox.restore();
    }
});

test("...", function() {
    // Arrange
    var someFunctionStub = this.sandbox.stub(MyView.prototype, 'someFunction');
    var options = { 
        foo: 'somevalue',
        model: new Backbone.Model()
    };
    this.sandbox.stub(options.model, 'on');
    
    // Act
    var instance = new MyView(options);
    
    // Assert
    ok(someFunctionStub.calledOnce);
    ok(instance.additionalCollection instanceof Backbone.Collection);
    strictEqual(instance.foo, options.foo);
    ok(options.model.on.calledWith('sync', instance.onModelSync));
});

Think Beyond Code Coverage

Unit tests help developers to not do evil things

Reusability
Limited scope of knowledge
Stop the nested anonymous functions!

Results

Organization
Maintainability
Presentation logic completely abstracted from the UI
Test coverage & ease of writing tests
Faster development

Thank you

Adam Terlson

adam@adamterlson.com

@adamterlson

Obligatory link slide

Backbone Fundamentals Project

Backbone Boilerplate

SinonJS

JSFiddle Testbed

setElement vs el-setting JSPerf

9 Tips for a clean BackboneJS App

By Adam Terlson

9 Tips for a clean BackboneJS App

This presentation seeks to eliminate that spaghettified, unmaintainable, untestable mess that JavaScript is so famous for producing and turn it into something beautiful. Developed after working on large teams with devs unfamiliar with JavaScript (not to mention Backbone) and yet tasked to create with it, I will walk through the 9 tips that I've found in practice will make your BackboneJS implementation easily maintained, easier to read, run better, and will allow you to effortlessly write those ever-so-important unit tests. Heavy on code samples, best practices, anti patterns, gotchyas, and random insights, this presentation is meant to serve as a reference point for creating a beautiful Backbone implementation for apps of any size and reduce the learning curve of BackboneJS.

4,667

Adam Terlson

Software Engineer

github.com/adamterlson

9 Tips for a clean BackboneJS App

@adamterlson

Why this presentation?

"Opportunities"

#1 : Organization Inside & Out

Outside is Obvious

What about Inside?

// Properties

// Properties

Warning: Use {} and [] wisely.

// Backbone

// Backbone (View)

//Backbone (Model)

// Bootstrap

// Rendering

// Rendering

//Backbone Events

//UI Events

// Methods

... they're functions

#2 : Consider "Bootstrap"

Goal

Common (Bad) Solutions

Solution

Initialize

Bootstrap

Usage

Benefits

#3 : Write Backbone, not jQuery

Why not jQuery?

Why not jQuery?

Render is your friend

...Most of the time

jQuery: Render, UI Events

Backbone: Everywhere else

#4 : Avoid Unnecessary Subviews

Signs to Separate

One way to subview

Multi Template/Render

#5 : Unidirectional Knowledge

Hierarchy

Via Promises (option 1)

Via Promises (option 2)

Via Events

#6 : Views Know el, Not The Live DOM

What's in the DIV?

Three steps to isolate your view from its context

Step 1: All selectors should be prefaced with this

this.$() ==> this.$el.find()

Timing

Context

Step 2: View's Creator decides placement

Good options

Bad options

Step 3: Use delegated eventing

Backbone events are delegated for you

What's in the DIV?

'initial text'

#7 : Don't cram everything in your view

View

Models should only know about data!

Model/Collection

Router

"It's too hard to unit

test JS code"

"Opportunities"

#8 : Arrange, Act, Assert

One Test to Rule Them All

Split tests up into three distinct parts

If you cannot fit your test into these parts in this order, write a second test.

In action (basic)

#9 : Write small unit tests

Unit testing with jQuery sucks

Isolate your unit with mocks

QUnit & Sinon Test Example

QUnit & Sinon Test Example: Initialize

Think Beyond Code Coverage

Results

Thank you

Obligatory link slide

#6 : Views Know `el`, Not The Live DOM

Step 1: All selectors should be prefaced with `this`