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About Yatin

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.

JavaScript Events Tutorial

Greetings readers, in this tutorial, we will show how to use the JavaScript Events.

1. Introduction

JavaScript is an object-oriented programming language that allows the client-side scripting to interact with a user and deliver the dynamic pages. Most web browsers including Google Chrome, Mozilla Firefox, Safari, Internet Explorer, Microsoft Edge, Opera, etc. support it. The JavaScript scripting language includes:

  • Declaring variables
  • Maintaining the retrieving values
  • Defining and invoking functions
  • Defining classes
  • Load and use external modules
  • Define event handlers
  • And much more ….

1.1 Advantages of JavaScript Language

The pros of using the JavaScript scripting language are:

  • JavaScript is easy to learn
  • It executes on client’s browser, so eliminates the server-side processing and be executed on any OS
  • JavaScript can be used with any type of web page e.g. PHP, ASP.NET, Perl etc
  • Web-page performance increases due to client-side execution
  • JavaScript code can be minified to decrease the loading time from the server
  • Many JavaScript-based application frameworks are available in the market to create Single page web applications e.g. AngularJS, ReactJS etc.

1.2 Disadvantages of JavaScript Language

The cons of using the JavaScript scripting language are:

  • No support for networking applications
  • Does not have any multi-threading or multi-processing capabilities
  • Does not allow the file reading and writing capabilities

1.3 Events in JavaScript

  • An event is a signal from the browser that something has happened or something that a user does.
  • For e.g.:
    • A webpage or an image has finished loading
    • An input field is changed
    • A button is clicked
    • Move the cursor over an HTML element
    • Submitting an HTML form
    • Keystrokes
  • Javascript language provides several ways to connect an event handler to an event. These ways are:
    • Using HTML tag attributes
    • Using DOM object property
    • Using special methods such as addeventlistener()

1.3.1 Common Events in JavaScript

There are sufficient javascript events available to make a webpage dynamic and clean. Here is the list of most common and popular javascript event handlers.

MethodDescription
onchangeOccurs when an HTML element is changed
onclickOccurs when the user clicks on an HTML element
onmouseoverOccurs when the user moves the mouse cursor over an HTML element
onmouseoutOccurs when the user moves the mouse cursor away from an HTML element
onkeydownOccurs when the user pushes a keyboard key
onloadOccurs when the current web page has finished loading

2. JavaScript Events Tutorial

Here is a systematic guide for implementing this tutorial using the JavaScript language.

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 us review the final project structure if you are confused about where you should create the corresponding files or folder later!

JavaScript Events - Application Project Structure

Fig. 1: Application Project Structure

2.3 Project Creation

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

JavaScript Events - Create a Maven Project

Fig. 2: Create a Maven Project

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

JavaScript Events - Project Details

Fig. 3: Project Details

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

JavaScript Events - Archetype Selection

Fig. 4: Archetype Selection

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

JavaScript Events - 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>com.javascript</groupId>
	<artifactId>JavaScriptEvents</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>war</packaging>
</project>

3. Application Building

Let us create an application to understand the basic building blocks of this tutorial.

3.1 Define the HTML

Let us write a simple index page in the JavaScriptEvents/src/main/webapp/ folder. Add the following code to it:

index.jsp

<!-- Javascript events tutorial -->
<div class="form-group">
	<div id="event">
		<h4 class="text-primary font-weight-bold">What is an event?</h4>
		<ol class="text-info line-hgt">
			<li>An event is a signal from the browser that something has happened or something that a user does</li>
			<li>For e.g.:
				<ul>
					<li>A webpage has finished loading</li>
					<li>An input field is changed</li>
					<li>A button is clicked</li>
				</ul>
			</li>
			<li>Javascript language provides several ways to connect an event handler to an event. These ways are:
				<ul>
					<li>Using HTML tag attributes</li>
					<li>Using DOM object property</li>
					<li>Using special methods such as <code>addeventlistener()</code></li>
				</ul>
			</li>
		</ol>
	</div>
	<!-- Input form -->
	<div id="code">
		<h4 class="text-sucess">Code Snippet</h4>
		<div> </div>
		<div id="myform">
			<div class="form-group">
				<label for="name">Name:</label>
				<input type="text" class="form-control" id="name" onblur="validate('name')">
			</div>
			<button id="btn_submit" type="button" class="btn btn-default" onmouseover="mouseover();" onmouseout="mouseout();" onclick="submit();">Submit</button>
		</div>
	</div>
</div>
<div> </div>

<!-- Result -->
<h5 id="result" class="text-info"></h5>

3.2 Define the JavaScript function

Let us write a simple javascript function that shows the events implementation in the javascript language. Add the following code to it:

JavaScript function

// Mouseover function
function mouseover() {
	var mover = document.getElementById("btn_submit");
	mover.style.background= 'blueviolet';
	mover.style.color= 'white';
}

// Mouseout function
function mouseout() {
	var mout = document.getElementById("btn_submit");
	mout.style.background= 'gainsboro';
	mout.style.color= 'black';
}

// Blur function
function validate(id) {
	var input = document.getElementById(id);
	if (input.value == "") {
		input.style.color= '#e52213';
		input.style.border= 'solid';
	} else {
		input.style.color= '#00ff99';
		input.style.border= 'solid';
	}
}

// Form submit function
function submit() {
	alert("Form submitted.");
}

3.3 First application

Complete the above steps and save the file. Let us see the sample code snippet.

index.jsp

<!DOCTYPE html>
<html lang="en">

<head>
    <title>Index page</title>
    <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">
    <style>
        #event,
        #code,
        #result {
            margin-left: 16px;
        }
        
        .line-hgt {
            line-height: 2.0;
        }
    </style>
</head>

<body>
    <div class="container">
        <h2 align="center" class="text-danger">Events in JavaScript</h2>
        <hr />

        <!-- Javascript events tutorial -->
        <div class="form-group">
            <div id="event">
                <h4 class="text-primary font-weight-bold">What is an event?</h4>
                <ol class="text-info line-hgt">
                    <li>An event is a signal from the browser that something has happened or something that a user does.</li>
                    <li>For e.g.:
                        <ul>
                            <li>A webpage has finished loading</li>
                            <li>An input field is changed</li>
                            <li>A button is clicked</li>
                        </ul>
                    </li>
                    <li>Javascript language provides several ways to connect an event handler to an event. These ways are:
                        <ul>
                            <li>Using HTML tag attributes</li>
                            <li>Using DOM object property</li>
                            <li>Using special methods such as <code>addeventlistener()</code></li>
                        </ul>
                    </li>
                </ol>
            </div>
            <!-- Input form -->
            <div id="code">
                <h4 class="text-sucess">Code Snippet</h4>
                <div> </div>
                <div id="myform">
                    <div class="form-group">
                        <label for="name">Name:</label>
                        <input type="text" class="form-control" id="name" onblur="validate('name')">
                    </div>
                    <button id="btn_submit" type="button" class="btn btn-default" onmouseover="mouseover();" onmouseout="mouseout();" onclick="submit();">Submit</button>
                </div>
            </div>
        </div>
        <div> </div>

        <!-- Result -->
        <h5 id="result" class="text-info"></h5>
    </div>
    <script>
    	// Mouseover function
        function mouseover() {
            var mover = document.getElementById("btn_submit");
            mover.style.background= 'blueviolet';
            mover.style.color= 'white';
        }

     	// Mouseout function
        function mouseout() {
            var mout = document.getElementById("btn_submit");
            mout.style.background= 'gainsboro';
            mout.style.color= 'black';
        }

     	// Blur function
        function validate(id) {
            var input = document.getElementById(id);
            if (input.value == "") {
                input.style.color= '#e52213';
                input.style.border= 'solid';
            } else {
                input.style.color= '#00ff99';
                input.style.border= 'solid';
            }
        }

     	// Form submit function
        function submit() {
            alert("Form submitted.");
        }
    </script>
</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 Tomcat7 server. To deploy the application on Tomat7, right-click on the project and navigate to Run as -> Run on Server.

JavaScript Events - 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 to display the application’s index page as shown in Fig. 7.

http://localhost:8082/JavaScriptEvents/

Server name (localhost) and port (8082) may vary as per your Tomcat configuration.

JavaScript Events - Index page

Fig. 7: Index page

That is all for this tutorial and I hope the article served you whatever you were looking for. Happy Learning and do not forget to share!

6. Conclusion

In this section, developers learned how to create a simple application with the JavaScript language. Developers can download the sample application as an Eclipse project in the Downloads section.

7. Download the Eclipse Project

This was an example of JavaScript Events for beginners.

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