AngularJS is a JavaScript-based open-source front-end web framework for developing single-page applications. It is maintained mainly by Google and a community of individuals and corporations. It aims to simplify both the development and the testing of such applications by providing a framework for client-side model–view–controller (MVC) and model–view–viewmodel (MVVM) architectures, along with components commonly used in web applications and progressive web applications.

AngularJS is used as the frontend of the MEAN stack, consisting of MongoDB database, Express.js web application server framework, AngularJS itself (or Angular), and Node.js server runtime environment.

The AngularJS framework is on Long Term Support (“LTS”) until December 31, 2021.^[3][4] After that date Google will no longer update AngularJS to fix security, browser compatibility, or jQuery issues.^[5][4] The Angular team recommends upgrading to Angular (v2+) as the best path forward, but they also provided some other options.^[6]

The AngularJS framework works by first reading the Hypertext Markup Language (HTML) page, which has additional custom HTML attributes embedded into it. Angular interprets those attributes as directives to bind input or output parts of the page to a model that is represented by standard JavaScript variables. The values of those JavaScript variables can be manually set within the code, or retrieved from static or dynamic JSON resources.

AngularJS is built on the belief that declarative programming should be used to create user interfaces and connect software components, while imperative programming is better suited to defining an application’s business logic.^[7] The framework adapts and extends traditional HTML to present dynamic content through two-way data-binding that allows for the automatic synchronization of models and views. As a result, AngularJS de-emphasizes explicit Document Object Model (DOM) manipulation with the goal of improving testability and performance.

AngularJS’s design goals include:

• to decouple DOM manipulation from application logic. The difficulty of this is dramatically affected by the way the code is structured.
• to decouple the client side of an application from the server-side. This allows development work to progress in parallel and allows for reuse of both sides.
• to provide structure for the journey of building an application: from designing the UI, through writing the business logic, to testing.

AngularJS implements the MVC pattern to separate presentation, data, and logic components.^[8] Using dependency injection, Angular brings traditionally server-side services, such as view-dependent controllers, to client-side web applications. Consequently, much of the burden on the server can be reduced.