Large Scale JavaScript applications

@alexbeletsky http://beletsky.net http://github.com/alexanderbeletsky

Big Credits to: Addy Osmani Addy Osmani is a rebel JavaScript blogger, speaker and a UI Developer for AOL (yes, we're still around!). He is also a member of the jQuery [Bug Triage/Docs/Front-end] teams where he assists with bugs, documentation and developer evangelism. His recent open-source projects include TodoMVC, which helps developers compare JavaScript MVC frameworks. For more on Addy’s work, check out his official website AddyOsmani.com for tutorials and magazines such as .net for his thoughts and commentaries on the state of the web.

JavaScript apps evolution

Early JavaScript application ● Mainly for web design ● Copy/Paste pattern commonly used ● Very poor browser support ● Lack of “community” knowledge base ● Low performace

Modern JavaScript application ● AJAX era started ● Adoption and respect by masses ● Huge improvement on standard and vendors ● Performance boosted ● New web assembly language ● Expertice & Best practices

Modern web app: GMail

Modern web app: Yandex Maps

Modern web app: Debitoor

“Modern web apps tend to be more (or equaly) complex on front end rather on back end”

In fact, JavaScript language is important... Front-end development could be complex...

What is Large scale app? “In my view, large-scale JavaScript apps are non- trivial applications requiring significant developer effort to maintain, where most heavy lifting of data manipulation and display falls to the browser.” - Addy Osmani

Complexity is handled by applying architectural approach

Patterns & Frameworks

Namespace Module Facade Mediator Observer

Namespace pattern “Namespacing is a technique employed to avoid collisions with other objects or variables in the global namespace” Goal: avoid names collision and provide facilities to organize blocks of functionality into easily managable groups

Namespace pattern implementation

Namespace Module Facade Mediator Observer

Module pattern “The module pattern is a popular design that pattern that encapsulates 'privacy', state and organization using closures” Goal: It provides a way of wrapping a mix of public and private methods and variables, protecting pieces from leaking into the global scope and accidentally colliding with another developer's interface

Module pattern implementation

Namespace Module Facade Mediator Observer

Facade pattern “ The facade pattern provides a convenient higher-level interface to a larger body of code, hiding its true underlying complexity. Think of it as simplifying the API being presented to other developers” Goal: to hide implementation-specific details about a body of functionality contained in individual modules. The implementation of a module can change without the clients really even knowing about it.

Facade pattern implementation

Facade pattern implementation Provides the open API for the rest of the application

Namespace Module Facade Mediator Observer

Mediator pattern “ The mediator is a behavioral design pattern that allows us to expose a unified interface through which the different parts of a system may communicate” Goal: promotes loose coupling by ensuring that instead of components referring to each other explicitly, their interaction is handled through this central point. This can help us decouple systems and improve the potential for component reusability.

Mediator pattern implementation

Facade pattern implementation Subscribe for particular event / Publish this event

Namespace Module Facade Mediator Observer

Observer pattern “ The Observer is a design pattern which allows an object (known as a subscriber) to watch another object (the publisher), where we provide a means for the subscriber and publisher form a listen and broadcast relationship” Goal: the promotion of loose coupling. Rather than single objects calling on the methods of other objects directly, they instead subscribe to a specific task or activity of another object and are notified when it occurs.

Observer pattern implementation https://gist.github.com/661855

Observer pattern implementation

RequireJS and AMD

RequireJS: file and module loader

RequreJS: Usage example

RequireJS: Main script

RequireJS uses Asynchronous Module Definition to load modules

AMD: module example

Putting thing together

Proposed Architecture Module Facade Mediator RequireJS AMD ● Loosely coupled ● Broken into independent modules ● Flexible (framework agnostic)

Demo application

backbone-aura

Further reading: ● Learning JavaScript Design Patterns http://addyosmani.com/resources/essentialjsdesignpatterns/book/ ● Patterns For Large-Scale JavaScript Application Architecture http://addyosmani.com/largescalejavascript ● Writing Modular JavaScript With AMD, CommonJS & ES Harmony http://addyosmani.com/writing-modular-js/ ● Scalable JavaScript Application Architecture http://www.youtube.com/watch?v=vXjVFPosQHw&feature=youtu.be

Thank you. http://beletsky.net @alexbeletsky