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Category: 01. Angular Js

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  • AngularJS Data Binding

    Data binding is a very useful and powerful feature used in software development technologies. It acts as a bridge between the view and business logic of the application.

    AngularJS follows Two-Way data binding model.

    One-Way Data Binding

    The one-way data binding is an approach where a value is taken from the data model and inserted into an HTML element. There is no way to update model from view. It is used in classical template systems. These systems bind data in only one direction.

    One Way Data Binding

    Two-Way Data Binding

    Data-binding in Angular apps is the automatic synchronization of data between the model and view components.

    Data binding lets you treat the model as the single-source-of-truth in your application. The view is a projection of the model at all times. If the model is changed, the view reflects the change and vice versa.

    Two Way Data Binding
    <!DOCTYPE html>  

<html>  

<script src="http://ajax.googleapis.com/ajax/libs/angularjs/1.4.8/angular.min.js"></script>  

<body>  

<div ng-app="" ng-init="firstName='Ajeet'">  

<p>Input something in the input box:</p>  

<p>Name: <input type="text" ng-model="firstName"></p>  

<p>You wrote: {{ firstName }}</p>  

</div>  

</body>  

</html>

    In the above example, the {{ firstName }} expression is an AngularJS data binding expression. Data binding in AngularJS binds AngularJS expressions with AngularJS data.

    {{ firstName }} is bound with ng-model=”firstName”.

    Let’s take another example where two text fields are bound together with two ng-model directives:

    <!DOCTYPE html>  

<html>  

<script src="http://ajax.googleapis.com/ajax/libs/angularjs/1.4.8/angular.min.js"></script>  

<body>  

<div data-ng-app="" data-ng-init="quantity=1;price=20">  

<h2>Cost Calculator</h2>  

Quantity: <input type="number" ng-model="quantity">  

Price: <input type="number" ng-model="price">  

<p><b>Total in rupees:</b> {{quantity * price}}</p>  

</div>  

</body>  

</html>

  • AngularJS First Example

    AngularJS applications are a mix of HTML and JavaScript. The first thing you need is an HTML page.

    <!DOCTYPE html>  

<html>  

<head>  

.  

.  

</head>  

<body>  

.  

.  

</body>  

</html> 

      Second, you need to include the AngularJS JavaScript file in the HTML page so we can use AngularJS:

      <!DOCTYPE html>  

<html>  

<head>  

  <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.5/angular.min.js"></script>  

</head>  

<body>  

.  

.  

</body>  

</html>  

        Note: You should always use the latest version of AngularJS, so it is not necessary to use the same version as the above example.

        AngularJS First Example

        Following is a simple “Hello Word” example made with AngularJS. It specifies the Model, View, Controller part of an AngularJS app.

        <!DOCTYPE html>  

<html lang="en">  

<head>  

    <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.5/angular.min.js"></script>  

</head>  

<body ng-app="myapp">  

<div ng-controller="HelloController" >  

<h2>Hello {{helloTo.title}} !</h2>  

</div>  

  

<script>  

angular.module("myapp", [])  

    .controller("HelloController", function($scope) {  

        $scope.helloTo = {};  

        $scope.helloTo.title = "World, AngularJS";  

    } );  

</script>  

</body>  

</html>

        View Part

        <div ng-controller="HelloController" >  

<h2>Hello {{helloTo.title}} !</h2>  

</div> 

          Controller Part

          <script>  

angular.module("myapp", [])  

    .controller("HelloController", function($scope) {  

        $scope.helloTo = {};  

        $scope.helloTo.title = "World, AngularJS";  

    });  

</script> 

          1. AngularJS MVC Architecture

            MVC stands for Model View Controller. It is a software design pattern for developing web applications. It is very popular because it isolates the application logic from the user interface layer and supports separation of concerns.

            AngularJS MVC Architecture

            The MVC pattern is made up of the following three parts:

            1. Model: It is responsible for managing application data. It responds to the requests from view and to the instructions from controller to update itself.
            2. View: It is responsible for displaying all data or only a portion of data to the users. It also specifies the data in a particular format triggered by the controller’s decision to present the data. They are script-based template systems such as JSP, ASP, PHP and very easy to integrate with AJAX technology.
            3. Controller: It is responsible to control the relation between models and views. It responds to user input and performs interactions on the data model objects. The controller receives input, validates it, and then performs business operations that modify the state of the data model.

          2. What is AngularJS

            Angular JS is an open source JavaScript framework that is used to build web applications. It can be freely used, changed and shared by anyone.

            Angular Js is developed by Google.

            It is an excellent framework for building single phase applications and line of business applications.

            Advantage of AngularJS

            There are a lot of JavaScript frameworks for building web applications. So, it is a genuine question, why to use Angular JS.

            Following are the advantages of AngularJS over other JavaScript frameworks:

            • Dependency Injection: Dependency Injection specifies a design pattern in which components are given their dependencies instead of hard coding them within the component.
            • Two way data binding: AngularJS creates a two way data-binding between the select element and the orderProp model. orderProp is then used as the input for the orderBy filter.
            • Testing: Angular JS is designed in a way that we can test right from the start. So, it is very easy to test any of its components through unit testing and end-to-end testing.
            • Model View Controller: In Angular JS, it is very easy to develop application in a clean MVC way. You just have to split your application code into MVC components i.e. Model, View and the Controller.

          3. Overview

            AngularJS is an open-source web application framework. It was originally developed in 2009 by Misko Hevery and Adam Abrons. It is now maintained by Google. Its latest version is 1.2.21.

            Definition of AngularJS as put by its official documentation is as follows −

            AngularJS is a structural framework for dynamic web applications. It lets you use HTML as your template language and lets you extend HTML’s syntax to express your application components clearly and succinctly. Its data binding and dependency injection eliminate much of the code you currently have to write. And it all happens within the browser, making it an ideal partner with any server technology.

            General Features

            The general features of AngularJS are as follows −

            • AngularJS is a efficient framework that can create Rich Internet Applications (RIA).
            • AngularJS provides developers an options to write client side applications using JavaScript in a clean Model View Controller (MVC) way.
            • Applications written in AngularJS are cross-browser compliant. AngularJS automatically handles JavaScript code suitable for each browser.
            • AngularJS is open source, completely free, and used by thousands of developers around the world. It is licensed under the Apache license version 2.0.

            Overall, AngularJS is a framework to build large scale, high-performance, and easyto-maintain web applications.

            Core Features

            The core features of AngularJS are as follows −

            • 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 bound to a particular scope.
            • Services − AngularJS comes with several built-in services such as $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 such as ngBind, ngModel, etc.
            • Templates − These are the rendered view with information from the controller and model. These can be a single file (such as index.html) or multiple views in one page using partials.
            • Routing − It is concept of switching views.
            • Model View Whatever − MVW is a design pattern for dividing an application into different parts called Model, View, and Controller, each with distinct responsibilities. AngularJS does not implement MVC in the traditional sense, but rather something closer to MVVM (Model-View-ViewModel). The Angular JS team refers it humorously as Model View Whatever.
            • Deep Linking − Deep linking allows 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 to create, understand, and test the applications easily.

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            Concepts

            The following diagram depicts some important parts of AngularJS which we will discuss in detail in the subsequent chapters.

            AngularJS Concepts

            Advantages of AngularJS

            The advantages of AngularJS are −

            • It provides the capability to create Single Page Application in a very clean and maintainable way.
            • It provides data binding capability to HTML. Thus, it gives 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, the developers can achieve more functionality with short code.
            • In AngularJS, views are pure html pages, and controllers written in JavaScript do the business processing.

            On the 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 a lot of merits, here are some points of concern −

            • Not 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 the user of your application disables JavaScript, then nothing would be visible, except the basic page.

            AngularJS Directives

            The AngularJS framework can be divided into 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.