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Yatin Batra
The author is graduated in Electronics & Telecommunication. During his studies, he has been involved with a significant number of projects ranging from programming and software engineering to telecommunications analysis. He works as a technical lead in the information technology sector where he is primarily involved with projects based on Java/J2EE technologies platform and novel UI technologies.

AngularJS ng-checked Directive Example

Hello readers, ng-checked in the angular library is a directive that reads the checked or unchecked status of the radio buttons and check-boxes. In this tutorial, we will see how this directive works in the angular library.

1. Introduction

AngularJS is a JavaScript MVC or Model-View-Controller framework developed by Google that lets developers build well structured, easily testable, and maintainable front-end applications. But before we start creating a real application using the angular library, let us see what the important parts of an angular application are.

1.1.1 Templates

In angular, a template is an HTML with added markups. The angular library compiles the templates and renders the resultant HTML page.

1.1.2 Directives

Directives are the markers (i.e. attributes) on a DOM element that tell angular to attach a specific behavior to that DOM element or even transform the DOM element and its children. Most of the directives in the angular library start with the ng. The directives consist of the following parts:

  • ng-app: The ng-app directive is a starting point. If the angular framework finds the ng-app directive anywhere in the HTML document, it bootstraps (i.e. initializes) itself and compiles the HTML template
  • ng-model: The ng-model directive binds an HTML element to a property on the $scope object. It also binds the values of angular application data to the HTML input controls
  • ng-bind: The ng-bind directive binds the angular application data to the HTML tags
  • ng-controller: The ng-controller directive specifies a controller in the HTML element. This controller will add behavior or support the data in that HTML element and its child elements
  • ng-repeat: The ng-repeat directive repeat a set of HTML elements for each item in a given collection
  • ng-checked: The ng-checked directive reads the checked or unchecked status of the radio buttons and check-boxes. This directive sets the value as ‘true’ or ‘false’ and has a priority of value 100

1.1.3 Expressions

An expression is like a JavaScript code usually wrapped inside the double curly braces such as {{ expression }}. The angular library evaluates the expression and produces a result.

These new APIs make developer’s life easier, really! But it would be difficult for a beginner to understand this without an example. Therefore, let us create a simple example using the angular library.

2. AngularJS ng-checked Directive Example

Here is a step-by-step guide for implementing the ng-checked directive in the angular web applications.

2.1 Tools Used

We are using Eclipse Kepler SR2, JDK 8 and Maven. Having said that, we have tested the code against JDK 1.7 and it works well.

2.2 Project Structure

Firstly, let’s review the final project structure if you are confused about where you should create the corresponding files or folder later!

Fig. 1: Application Project Structure

Fig. 1: Application Project Structure

2.3 Project Creation

This section will show how to create a Java-based Maven project with Eclipse. In Eclipse Ide, go to File -> New -> Maven Project.

Fig. 2: Create Maven Project

Fig. 2: Create Maven Project

In the New Maven Project window, it will ask you to select project location. By default, ‘Use default workspace location’ will be selected. Just click on next button to proceed.

Fig. 3: Project Details

Fig. 3: Project Details

Select the ‘Maven Web App’ Archetype from the list of options and click next.

Fig. 4: Archetype Selection

Fig. 4: Archetype Selection

It will ask you to ‘Enter the group and the artifact id for the project’. We will enter the details as shown in the below image. The version number will be by default: 0.0.1-SNAPSHOT.

Fig. 5: Archetype Parameters

Fig. 5: Archetype Parameters

Click on Finish and the creation of a maven project is completed. If you see, it has downloaded the maven dependencies and a pom.xml file will be created. It will have the following code:

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>AngularJsNgCheckedEx</groupId>
	<artifactId>AngularJsNgCheckedEx</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>war</packaging>
</project>

3. Application Building

Let’s start building an application to understand the basic building blocks of this tutorial in the angular library.

3.1 Load the Angular framework

Since it is a pure JavaScript framework, we should add its reference using the <script> tag.

<script type="text/javascript" src="resource/js/angular_v1.6.0.js"></script>

3.2 Define the Angular application

Next, we will define the angular application using the <ng-app> and <ng-controller> directives.

index.jsp

<div ng-app="myApp" ng-controller="myCtrl">
 ...
</div>

3.3 Define the Angular Controller

The JavaScript file i.e. controller.js includes the myCtrl function as the “controller” in the Model-View-Controller. This JavaScript code has the random employee details stored in an array format and the delete() function that drops the selected employee records. Do note, the angular function will be executed on the $scope objects through a button click.

controller.js

var mainApp = angular.module("myApp", []);

mainApp.controller('myCtrl', ['$scope', function ($scope) {
	var arr = [];
	$scope.empList = [ { id: '101', fName: 'John', lName: 'Gordon' }, { id: '102', fName: 'Smith', lName: 'Bing' }, { id: '103', fName: 'Allen', lName: 'Ross' }, { id: '104', fName: 'Marry', lName: 'Potter' }, { id: '105', fName: 'Jennifer', lName: 'White' } ];
	$scope.getIndex = function (id, isTrue) {
		if (isTrue) {
			arr.push(id);
		}			
		else {
			var index = arr.indexOf(id);
			arr.splice(index, 1);
		}
	};
	$scope.delete = function (isMaster) {
		if (isMaster) {
			$scope.empList = [];
		}
		else {
			for (var i = 0; i < arr.length; i++) {
				var rec = $scope.empList.filter(function (p) { 
					return p.id == arr[i] 
				});
				var idx = $scope.empList.indexOf(rec[0]);
				$scope.empList.splice(idx, 1);
			}
		};
		arr = [];
	};
}]);

3.4 Complete Application

In this example, we have an employee table with a check-box for each employee record. On a button click, the record will be dropped for the selected (i.e. checked) check-box. Also, there is a master check-box for selecting all records and dropping them at once. Complete the above steps to understand the usage.

index.jsp

<!DOCTYPE html>
<html>
   <head>
      <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
      <title>AngularJS ng-Checked Directive Example</title>
      
      <!-- AngularJs Javascript File -->
      <script type="text/javascript" src="resource/js/angular_v1.6.0.js"></script>
      <script type="text/javascript" src="resource/js/controller.js"></script>
      
      <!-- Bootstrap Css -->
      <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css">
      <link rel="stylesheet" href="resource/css/controller.css">      
   </head>
   <body>
      <div id="angularCheckedExample" class="container">
         <h1 align="center" class="text-primary">AngularJS - ng-Checked Directive Example</h1>
         <hr />
         <!------ ANGULAR JAVASCRIPT 'ng-Directive' EXAMPLE ------>
         <div ng-app="myApp" ng-controller="myCtrl">
            <div class="container">
               <div class="input-group">
                  <label>Delete all: </label><input id="delMasterCheckBox" type="checkbox" ng-model="masterCheckBox" />
                  <sup class="text-info position">Click "Delete all" to select all employees</sup>
                  
                  <!------ DELETE BUTTON ------>
                  <div class="input-group-btn">
                     <button id="dBtn" type="button" class="btn btn-danger" ng-click="delete(masterCheckBox)">Delete</button>
                  </div>
               </div>
               
               <!------ EMPLOYEE LIST ------>
               <div> </div>
               <table class="table table-hover pointer">
                  <thead>
                     <tr>
                        <th>Id</th>
                        <th>First Name</th>
                        <th>Last Name</th>
                        <th>Action</th>
                     </tr>
                  </thead>
                  <tbody>
                     <tr ng-repeat="e in empList">
                        <td>{{ e.id }}</td>
                        <td>{{ e.fName }}</td>
                        <td>{{ e.lName }}</td>
                        <td>
                           <input id="delCheckBox" type="checkbox" ng-checked="masterCheckBox" ng-model="isTrue" ng-change="getIndex(e.id, isTrue)" />
                        </td>
                     </tr>
                  </tbody>
               </table>
            </div>
         </div>
      </div>
   </body>
</html>

4. Run the Application

As we are ready for all the changes, let us compile the project and deploy the application on the tomcat server. To deploy the application on Tomat7, right-click on the project and navigate to Run as -> Run on Server.

Fig. 6: How to Deploy Application on Tomcat

Fig. 6: How to Deploy Application on Tomcat

Tomcat will deploy the application in its web-apps folder and shall start its execution to deploy the project so that we can go ahead and test it in the browser.

5. Project Demo

Open your favorite browser and hit the following URL. The output page having the default employee list will be displayed.

http://localhost:8080/AngularJsNgCheckedEx/

Server name (localhost) and port (8080) may vary as per your Tomcat configuration.

Fig. 7: Default application page

Fig. 7: Default application page

Here we have the delete() function attached to a button click. This angular function will drop the selected employee records as shown below.

Fig. 8: Selected record deleted

Fig. 8: Selected record deleted

That’s all for this post. Happy Learning!!

6. Conclusion

In this section, developers learned how to create a simple application using the ng-checked directive. Developers can download the sample application as an Eclipse project in the Downloads section.

7. Download the Eclipse Project

This was an example of the ng-checked directive in the angular library.

Download
You can download the full source code of this example here: AngularJsNgCheckedEx
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