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Introduction to AngularJS

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  • Last Updated : 09 Aug, 2022

AngularJS is a Javascript open-source front-end structural framework that is mainly used to develop single-page web applications(SPAs). It is a continuously growing and expanding framework which provides better ways for developing web applications. It changes the static HTML to dynamic HTML. Its features like dynamic binding and dependency injection eliminate the need for code that we have to write otherwise. AngularJS is rapidly growing and because of this reason, we have different versions of AngularJS with the latest stable being 1.7.9. It is also important to note that Angular is different from AngularJS. It is an open-source project which can be freely used and changed by anyone. It extends HTML attributes with Directives, and data is bound with HTML.

History of AngularJS: AngularJS was originally developed in 2008-2009 by Miško Hevery and Adam abrons at Brat Tech LLC, as software for the online JSON storage service, in order to ease to development of the applications for the enterprise, that has been valued by the megabyte. It is now maintained by Google. AngularJS was released with version 1.6, which contains the component-based application architecture concept. This release version removed the Sandbox, which facilitates the security, despite having the various vulnerabilities that have evolved, which bypassed the sandbox.

Why use AngularJS?

  • Easy to work with: All you need to know to work with AngularJS is the basics of HTML, CSS, and Javascript, not necessary to be an expert in these technologies.
  • Time-saving: AngularJs allows us to work with components and hence we can use them again which saves time and unnecessary code.
  • Ready to use a template: AngularJs is mainly plain HTML, and it mainly makes use of the plain HTML template and passes it to the DOM and then the AngularJS compiler. It traverses the templates and then they are ready to use.

Key Features: There are numerous features of AngularJS that contribute to creating efficient applications. Some of the features are described below:

  • Model View Controller(MVC): An architecture is basically a software pattern used to develop an application. It consists of three components: 
    • Model: This component consists of a database & is responsible for managing the data & logic of the application. It responds to the request made by the View component & the instruction given by the Controller component, in order to update itself.
    • View: This component is responsible for displaying the application data to the users. The View is basically the user interface that helps to render the required data to the user, with the help of the AngularJS expressions.
    • Controller: This component is responsible for communicating & interacting between the Model & the View Component, i.e. its main job is to connect the model and the view component. It helps to validate the input data by implementing some business logic that manipulates the state of the data model.

Normally, when we talk about MVC architecture, we have to split our applications into these three components and then write the code to connect them. However, in AngularJS, all we have to do is split the application into MVC and it does the rest by itself. It saves a lot of time and allows you to finish the job with less code. 

  • Data Model BindingData Binding in AngularJS is a two-way process, i.e the view layer of the MVC architecture is an exact copy of the model layer. You don’t need to write special code to bind data to the HTML controls. Normally, in other MVC architectures, we have to continuously update the view layer and the model layer to remain in sync with one another. In AngularJs it can be said that the model layer and the view layer remain synchronized with each other. Like when the data in the model changes, then the view layer reflects the change and vice versa. It happens immediately and automatically which helps in making sure that the model and the view are updated at all times. 
  • Templates: The main advantage of using AngularJS is how it makes use of the templates. Normally what happens is that the templates are passed by the browser into DOM, then DOM becomes the input of the AngularJS compiler and then AngularJS traverses the DOM template for rendering instructions which are called directives. The other siblings of AngularJS work differently as they make use of the HTML String whereas AngularJs does not manipulate the template strings. Using the DOM is what gives us the privilege to extend the directive vocabulary or even abstract them into reusable components.
  • Unit Testing ready: The concern of Google’s designer was not only to develop Angular but also to develop a testing framework called “Karma” which helps in designing unit tests for AngularJS applications. 

Benefits of AngularJS:

Depending Injection: Dependency Injection is a software design pattern. It works on the basis of Inversion of Control. Inversion control means objects do not create other objects. Instead, they get these objects from an outside source. The dependent object is not created by the primary object after that then uses its methods. Instead, an external source creates the dependent object and gives it to the source object for further usage. On the basis of dependency injection, we create a service to acquire all the information from the database and get into the model class. 

In Angular.JS, dependencies are injected by using an “injectable factory method” or “constructor function”. These components can be injected with “service” and “value” components as dependencies. The $http service is normally defined from within the controller in the following manner.

sampleApp.controller ('AngularJSController', function ($scope, $http)

Example: This example illustrates the basic Angular JS by implementing the directive, controller, etc.

HTML




<!DOCTYPE html>
<html>
  
<head>
    <title>AngularJS Example</title>
    <script src=
    </script>
</head>
  
<body>
    <center>
        <h1 style="color:green">
            GeeksforGeeks
        </h1>
        <h3>AngularJS Example</h3>
        <div ng-app="myApp" 
             ng-controller="myCtrl"
             ng-style="gfgObj">
            <input type="text" 
                   ng-model="comName">
            <input type="text" 
                   ng-model="detail">
            <br> {{comName + " "+detail }}
        </div>
    </center>
    <script>
        var app = angular.module('myApp', []);
        app.controller('myCtrl', function($scope) {
            $scope.comName = "GeeksforGeeks";
            $scope.detail = "Learning Together!"
            $scope.gfgObj = {
                "color": "green",
                "font-family": "sans-serif",
                "font-size": "25px"
            }
        });
    </script>
</body>
</html>


Output:

 

Pros of AngularJS:

  • It facilitates the Two-way Binding that helps to render correspondingly the changes made to the view or the model.
  • It helps to create the responsive web application, along with providing the prototyping that can be utilized to load the application faster.
  • It uses the concept of directive that helps to add the functionality to the application. For this, the overall length of the code reduces along with discarding the repetition of the code that is specific to perform the particular task.

Cons of AngularJS:

  • As this framework belongs to Javascript, so it is required to have prior knowledge of Javascript.
  • If new to this framework, then the debugging the scope can be difficult task.

My Personal Notes arrow_drop_up
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