AngularJS is a JavaScript framework that is used in Single Page Application (SPA) projects. It extends HTML DOM with additional attributes and makes it more responsive to user actions. AngularJS is open source, completely free, and used by thousands of developers around the world. AngularJS provides developers options to write client side application (using JavaScript) in a clean MVC(Model View Controller) way. Its ability to be cross-browser compliant lets it handle code suitable for each browser.
It can be added to any HTML page with a <script> tag. It extends HTML attributes with directives, and binds data to HTML with expressions.
Simple Example:
<!DOCTYPE html>
<html lang="en-US">
<script src="http://ajax.googleapis.com/ajax/libs/angularjs/1.4.8/angular.min.js"></script>
<body>
<div ng-app="">
<p>Name : <input type="text" ng-model="name"></p>
<h1>Hello {{name}}</h1>
</div>
</body>
</html>
Following are most important core features of AngularJS:
Data-binding − It is the automatic synchronization of data between model and view components.
Scope − These are objects that refer to the model. They act as a glue between controller and view.
Controller − These are JavaScript functions that are bound to a particular scope.
Services − AngularJS come with several built-in services for example $http to make a XMLHttpRequests. These are singleton objects which are instantiated only once in app.
Filters − These select a subset of items from an array and returns a new array.
Directives − Directives are markers on DOM elements (such as elements, attributes, css, and more). These can be used to create custom HTML tags that serve as new, custom widgets. AngularJS has built-in directives (ngBind, ngModel...)
Templates − These are the rendered view with information from the controller and model. These can be a single file (like index.html) or multiple views in one page using "partials".
Deep Linking − Deep linking allows you to encode the state of application in the URL so that it can be bookmarked. The application can then be restored from the URL to the same state.
Dependency Injection − AngularJS has a built-in dependency injection subsystem that helps the developer by making the application easier to develop, understand, and test.
Following diagram depicts some important parts of AngularJS which we will discuss in detail in the subsequent chapters.
Advantages of AngularJS
AngularJS provides capability to create Single Page Application in a very clean and maintainable way.
AngularJS provides data binding capability to HTML thus giving user a rich and responsive experience.
AngularJS code is unit testable.
AngularJS uses dependency injection and make use of separation of concerns.
AngularJS provides reusable components.
With AngularJS, developer write less code and get more functionality.
In AngularJS, views are pure html pages, and controllers written in JavaScript do the business processing.
On top of everything, AngularJS applications can run on all major browsers and smart phones including Android and iOS based phones/tablets.
Disadvantages of AngularJS
Though AngularJS comes with lots of plus points but same time we should consider the following points:
Less Secure − Being JavaScript only framework, application written in AngularJS are not safe. Server side authentication and authorization is must to keep an application secure.
Not degradable − If your application user disables JavaScript then user will just see the basic page and nothing more.
The AngularJS Components
The AngularJS framework can be divided into following three major parts:
ng-app − This directive defines and links an AngularJS application to HTML.
ng-model − This directive binds the values of AngularJS application data to HTML input controls.
ng-bind − This directive binds the AngularJS Application data to HTML tags.
AngularJS is a relatively new JavaScript framework by Google, designed to make your front-end development as easy as possible. It is built and maintained by dedicated Google engineers. It means you not only have a large open community to learn from, but you also have skilled engineers tasked to help you get your Angular questions answered. AngularJS ensures that no other plugins or frameworks are needed to build a data-driven web application.
