How AngularJS Embraced Traditional Design Patterns

How Angular Embraced
Traditional OOP Design
Patterns

Ran Mizrahi (@ranm8)

Open Source Dpt. Leader @ CodeOasis

About CodeOasis

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CodeOasis specializes in cutting-edge web solutions.

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Large variety of customers (from startups to enterprises).

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We’re passionate about JavaScript (-:

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Technologies we love:

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Play Framework

AngularJS

nodeJS

HTML5

CSS3

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Our Microsoft department works with C#, WPF, etc.

Implementing
Design Patterns in
JavaScript

Implementing Design Patterns in JavaScript
Most traditional object-oriented languages

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Classes.

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Interfaces.

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Inheritance.

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Encapsulation.

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Polymorphism.

We don’t have classes…
var User = new Class({
initialize: function(name) {
this.name = name;
},
setEmail: function(mail) {
this.mail = mail;
}
});
!
var someUser = new User('Ran Mizrahi');
* MooTools Example

We don’t have interfaces…

var DynamicMap = new Interface('DynamicMap', ['centerOnPoint', 'zoom',
'draw']);

!

function displayRoute(mapInstance) {
Interface.ensureImplements(mapInstance, DynamicMap);

!

mapInstace.centerOnPoint(12, 34);
mapInstace.draw(5);
mapInstace.zoom();
}
* Taken from the book “Pro JavaScript Design Patterns”

We don’t have classical inheritance..
var User = new Class({
!
extends: BaseUser,
initialize: function(name) {
this.name = name;
},
setEmail: function(mail) {
this.mail = mail;
}
});
!
var someUser = new User('Ran Mizrahi');
* MooTools Example

Learning To Embrace JavaScript

“When I see a bird that walks
like a duck and sounds like a
duck, I call that bird a duck”
— James Whitcomb Riley


This is how a duck looks like…

function isWindow(obj) {
return obj && obj.document && obj.location
&& obj.alert && obj.setInterval;
}
* Angular implementation of the isWindow method…

JavaScript is simple (can be explained over a beer) and
makes us write less code…
Java:!
List<Book> books = new ArrayList<Book>();!

!

JavaScript:!
var books = [];!

Object is a unit responsible for state and behaviour and
JavaScript function has them both.
function Unit() {
var state;
!
function behaviour() {
// Some behaviour
}

}

return function() {
// Do something
}

We don’t have visibility keywords (e.g. private, protected,
public) but we do have closures
var Service = (function(window, undefined) {
// Private
function base64Encode(string) {
return window.btoa(string);
}
// Public
return {
encode: function(string) {
return base64Encode(string);
}
};
}(window));

State management can be as easy by using constructor
functions or closures…
function someFunction(baseUrl) {
var config = {
url: baseUrl
};

};

return function() {
return config.url + '/hey';
}

function Duck(name) {
// Object state
this.name = name;
}

Polymorphism can be beautiful without interfaces, if it’s just a
duck…
function Duck() {
// Private state here…

!

function Bird() {
// Private state here…

!

// Public state
return {
walk: function() {
// Walk like a duck
return quack();
},

// Public state
return {
walk: function() {
// Walk like a bird
return tweet();
},

talk: function() {
// Talk like a duck
}

talk: function() {
// Talk like a bird
}

};
}

};
}
function talker(someBird) {
// Make it talk
someBird.talk();
}

But what will happen if the duck won’t talk…

JavaScript has prototypical inheritance but yet, I don’t often
feel I need to inherit anything (prefer polymorphic composition
over inheritance).

For true coverage and conﬁdence, compilers won’t do the job
and they can’t replace real unit test coverage.

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Almost everything is mutable.

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Easily stub anything.

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Easily fake dependencies.

MVC and Controllers
angular.module('myModule')
.controller('MyCtrl', ['$http', MyCtrl]);
!
// Dependencies are in closure (-:
function MyCtrl($http) {
var someState = {};

}

function doSomething() {
// Closure is accessible.
}

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Controllers are just JavaScript function.  

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They can encapsulate and preserve state by using closures.

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Exposes behaviour with $scope.

Dependency Injection
.controller('MyCtrl', ['$http', MyCtrl]);
function MyCtrl($http) {
$http.get('http://google.com').then(getTheMonkey);
}

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Simple dynamic dependency injection based on arrays and
naming convention.  

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Makes your code polymorphic by easily replacing your
implementation.

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Super easy to isolate and test.

Decorator
Decorator is a pattern used to “decorate” functionality of
certain object.

Decorator
Angular made service decoration really easy…
$provider.decorator('$log', ['delegate', function(delegate) {
// Convert warning to error
delegate.warn = delegate.error;
// Return the decorated service
return delegate;
}]);

Ask for a function, manipulate it and return a new one (-:

Facade
A facade is an object that provides a simpliﬁed interface to a
larger body of code and logic.
.factory('ReallyComplicatedService', [Service]);

!

function Service($http) {
// Do all the private stuff and handle the other library
// Expose really simple interface
return {
get: function() {
// Get it
},
del: function() {
// Delete it
}
};
}

Singleton
Singletons is a design pattern that restricts the instantiation of
a class to one object.
var Singleton = (function() {
function privateFunction() {
// Do private stuff
}
return {
someMethod: function() {
// Do public stuff
},
anotherMethod: function() {
// Do some more public stuff
}

};
}());

JavaScript makes singleton really easy (-:  
But still, it’s global and hard to conﬁgure…

Singleton
Angular used it and provided us with dependency injection to
avoid singleton downsides among others.
.provider('myHttp', myHttp);
function myHttp() {
var baseUrl;
this.baseUrl = function(value) {
if (!value) {
return baseUrl;
}
};

}

baseUrl = value;

this.$get = ['$q', function() {
// myHttp service implementation...
}];

How AngularJS Embraced Traditional Design Patterns

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