AngularJS is a JavaScript-based open-source front-end web application framework mainly maintained by Google and by a community of individuals and corporations to address many of the challenges encountered in developing single-page applications.

why you should be using Angular today.
1. MVC done right
Most frameworks implement MVC by asking you to split your app into MVC components, then require you to write code to string them up together again. That’s a lot of work. Angular implements MVC by asking you to split your app into MVC components, then just let Angular do the rest. Angular manages your components for you and also serves as the pipeline that connects them.

2. A declarative user interface.
Angular uses HTML to define the app’s user interface. HTML is a declarative language which is more intuitive and less convoluted than defining the interface procedurally in JavaScript. HTML is also less brittle to reorganize than an interface written in JavaScript, meaning things are less likely to break. Plus you can bring in many more UI developers when the view is written in HTML.

3. Data models are POJO
Data models in Angular are plain old JavaScript objects (POJO) and don’t require extraneous getter and setter functions. You can add and change properties directly on it and loop over objects and arrays at will. Your code will look much cleaner and more intuitive, the way mother nature intended.

4. Behavior with directives
Directives are Angular’s way of bringing additional functionality to HTML. Imagine a world where HTML has so many rich elements that we never have to manipulate the DOM to simulate them. All that our app needs to do is to assign attributes to elements to get any functionality out of the box.

5. Flexibility with filters
Filters filter the data before they reach the view and can involve something as simple as formatting decimal places on a number, reversing the order of an array, filtering an array based on a parameter, or implementing pagination. Filters are designed to be standalone functions that are separate from your app, similar to Directives, but are only concerned with data transformations.

6. Write less code
All the points up till now mean that you get to write less code. You don’t have to write your own MVC pipeline. The view is defined using HTML, which is more concise. Data models are simpler to write without getters/setters. Data-binding means you don’t have to put data into the view manually. Since directives are separate from app code, they can be written by another team in parallel with minimal integration issues. Filters allow you to manipulate data on the view level without changing your controllers.

7. DOM manipulations where they belong
Traditionally, the view modifies the DOM to present data and manipulates the DOM (or invokes jQuery) to add behavior. With Angular, DOM manipulation code should be inside directives and not in the view. Angular sees the view as just another HTML page with placeholders for data. This way of looking at the view pairs nicely with user interface designers.

8. Service providers where they belong
Controllers in Angular are simple functions that have one job only, which is to manipulate the scope. For example, you can use it to prefill data into the scope from the server or implement business logic validations. Unlike other frameworks, controllers are not objects and don’t inherit from anything.

9. Context aware communication
A PubSub system is a pretty common tool that allows for decoupled communication. Most PubSub implementations on the web are not context aware. Sometimes you want a PubSub message to be readable only by children of a particular node, or only readable by the ancestors of a particular child. In other words, sometimes you don’t want unrelated MVC components to be reading your messages.

10. Unit testing ready
What description of Angular would be complete without talking about it’s unit testing readiness? The whole of Angular is linked together by Dependency Injection (DI). It’s what it uses to manage your controllers and scopes. Because all your controllers depend on DI to pass it information, Angular’s unit tests are able to usurp DI to perform unit testing by injecting mock data into your controller and measuring the output and behavior. In fact, Angular already has a mock HTTP provider to inject fake server responses into controllers.