Angular JS
Technology - Angular JS
AngularJS
AngularJS is an open-source JavaScript framework developed by Google for building dynamic web applications. It is used to simplify the development and testing of single-page applications (SPAs) by providing a structure for client-side code. While AngularJS was widely used, it has been largely succeeded by Angular (often referred to as “Angular 2+” or simply “Angular”), which is a complete rewrite of AngularJS, offering better performance and more features. However, AngularJS still holds significance for legacy projects.
Key Features of AngularJS:
- MVC Architecture:
AngularJS uses a Model-View-Controller (MVC)architecture, which helps separate concerns:- Model: Represents the application data.
- View: Displays the data (UI).
- Controller: Handles the logic and links the model and view.
- Two-Way Data Binding:
One of the standout features of AngularJS is two-way data binding, which means any change in the UI (view) automatically updates the model (data), and any change in the model updates the UI. This eliminates the need for manually updating the view when the model changes. - Directives:
Directives are special markers in the HTML code that tell AngularJS to attach specific behavior to an element or manipulate its DOM (Document Object Model). For example:- ng-model: Binds an input field to a model.
- ng-repeat: Repeats an HTML element for each item in a list.
- ng-if: Conditionally includes or excludes an HTML element.
- Dependency Injection:
AngularJS provides dependency injection, which makes it easier to manage the relationships between components and services. It helps in writing modular, reusable, and testable code. - Filters:
Filters in AngularJS are used to format the data before displaying it in the view. For example, you can use filters to format dates, currency, or even manipulate arrays. - Services:
AngularJS uses servicesto provide reusable business logic and shared functionality across different components (controllers, directives, etc.). Services can be created to handle tasks like HTTP requests or session management. - Routing:
The AngularJS routingmodule allows the application to switch between different views (or templates) without requiring a full page reload. This is particularly useful for building single-page applications (SPAs). - Templating:
AngularJS provides a powerful templating system that allows you to define HTML with embedded AngularJS expressions. These expressions can be used to display data dynamically, bind input fields, and manipulate DOM elements. - Testability:
AngularJS was built with testability in mind. It supports both unit testing and end-to-end testing with tools like Karma(a test runner) and Jasmine (a testing framework).
Example of AngularJS Code:
<!DOCTYPE html>
<html ng-app=”myApp”>
<head>
<script src=”https://ajax.googleapis.com/ajax/libs/angularjs/1.8.2/angular.min.js“></script>
</head>
<body>
<div ng-controller=”myController”>
<h1>{{ greeting }}</h1>
<input ng-model=”name” placeholder=”Enter your name”>
<p>Hello, {{ name }}!</p>
</div>
<script>
var app = angular.module(‘myApp’, []);
app.controller(‘myController’, function($scope) {
$scope.greeting = ‘Welcome to AngularJS!’;
$scope.name = ”;
});
</script>
</body>
</html>
Explanation:
- The ng-app directive initializes the AngularJS application.
- The ng-controller directive attaches a controller to a section of the HTML.
- The ng-model directive binds an input field to the model (name).
- The {{ greeting }} and {{ name }} expressions display dynamic data.
Transition to Angular (Angular 2+):
In 2016, AngularJS was replaced by Angular 2 (now known as just Angular), which introduced major improvements such as:
- TypeScriptas the primary language for development (instead of JavaScript).
- A more modular architecture.
- Enhanced performance, including a more efficient change detection mechanism.
- Improved tooling, such as the Angular CLI (Command Line Interface).
Key Differences Between AngularJS and Angular:
- Language: AngularJS uses JavaScript, while Angular uses TypeScript.
- Performance: Angular is faster and more efficient due to its improved change detection mechanism and better tooling.
- Architecture: Angular uses components instead of controllers, following a more modern and modular architecture.
- Mobile Support: Angular has better support for mobile applications compared to AngularJS.
Conclusion:
AngularJS was a revolutionary framework for its time, enabling developers to build dynamic and interactive web applications. However, with the release of Angular (2+), many developers transitioned to the newer version due to its better performance, modern features, and scalability. Despite this, AngularJS remains important in legacy projects, and understanding it can still be valuable for maintaining and updating older applications.