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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 Fetch Example

Greetings readers, in this tutorial, we will show the JavaScript Fetch API.

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 Fetch API in JavaScript

  • In javascript, Fetch API is an interface to fetch the resources from the server
  • Fetch API uses promises to support the asynchronous programming by making the code look synchronous and avoiding problems associated with callbacks
  • The fetch() method allows the developers to make the network requests similar to XMLHttpRequest (XHR)
  • The fetch() method is defined on a window object, which developers use to perform requests and sent it to a server
  • The fetch() method accepts only resource url as a mandatory argument

2. JavaScript Fetch Example

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 Fetch - 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 Fetch - 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 Fetch - Project Details

Fig. 3: Project Details

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

JavaScript Fetch - 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 Fetch - 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>JavascriptFetchApi</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 JavascriptFetchApi/src/main/webapp/ folder. Add the following code to it:

index.jsp

<!-- Javascript fetch() method tutorial -->
<h6 class="text-info">Click the button to fetch the data from the server.</h6>
<div> </div>

<button id="btn_submit" type="button" class="btn btn-success" onclick="fetchProduct();">Fetch</button>
<div> </div>

<ul id="product"></ul>

3.2 Define the JavaScript function

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

JavaScript function

var ul = document.getElementById("product");
const url = "<-- Enter url to fetch the resources from the server -->";

// Function to fetch the data from the server.
function fetchProduct() {
	fetch(url).then((res) => res.json()).then((json) => {
		console.log(json);
		for(var i=0; i < json.items.length; i++) {
			var li = document.createElement("li");
			li.appendChild(document.createTextNode(json.items[i].name));
			ul.appendChild(li);
		}
	});
}

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">
</head>

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

        <!-- Javascript fetch() method tutorial -->
		<h6 class="text-info">Click the button to fetch the data from the server.</h6>
		<div> </div>
		
		<button id="btn_submit" type="button" class="btn btn-success" onclick="fetchProduct();">Fetch</button>
		<div> </div>
		
		<ul id="product"></ul>
    </div>
    <script>
		var ul = document.getElementById("product");
		const url = "<-- Enter url to fetch the resources from the server -->";
		
		// Function to fetch the data from the server.
		function fetchProduct() {
			fetch(url).then((res) => res.json()).then((json) => {
				console.log(json);
				for(var i=0; i < json.items.length; i++) {
					var li = document.createElement("li");
li.appendChild(document.createTextNode(json.items[i].name));
					ul.appendChild(li);
				}
			});
		}
    </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 Fetch - 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/JavascriptFetchApi/

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

JavaScript Fetch - Index page

Fig. 7: Index page

Developers can click the Fetch button to fetch the data from the server as shown in fig. 8.

JavaScript Fetch - Fetch API in JavaScript

Fig. 8: Fetch API in JavaScript

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 Fetch example for the beginners.

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