AJAX and JSON with JavaScript

Learn how to work with AJAX and JSON in JavaScript with our comprehensive guide. Explore the theory and multiple code examples to help you understand how it works. Perfect for beginners!

Updated: March 11, 2023

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AJAX and JSON are two important technologies in web development that allow for dynamic and responsive user experiences. In this article, we’ll explore how they work in JavaScript and how you can use them to build modern web applications.

What is AJAX?

AJAX stands for Asynchronous JavaScript and XML, and it’s a technique used in web development to create dynamic, interactive web pages. With AJAX, you can send and receive data asynchronously without needing to refresh the entire page. This makes for a more seamless user experience and can greatly improve the performance of your web applications.

To implement AJAX in JavaScript, you’ll typically use the XMLHttpRequest object, which allows you to send HTTP requests and receive responses without reloading the entire page. Here’s an example of how to use the XMLHttpRequest object to retrieve data from a server:

const xhr = new XMLHttpRequest(); xhr.open('GET', 'https://example.com/data'); xhr.onload = function() < if (xhr.status === 200) < const data = JSON.parse(xhr.responseText); // do something with the data > >; xhr.send();

What is JSON?

JSON stands for JavaScript Object Notation, and it’s a lightweight data interchange format that’s easy for humans to read and write, and easy for machines to parse and generate. JSON is often used to transmit data between a server and a web application, and it’s become the de facto standard for data exchange on the web.

In JavaScript, you can use the JSON object to encode and decode JSON data. Here’s an example of how to use the JSON object to encode an object to JSON:

const data = < name: 'John', age: 30, email: 'john@example.com' >; const jsonData = JSON.stringify(data); console.log(jsonData); //

And here’s an example of how to use the JSON object to decode JSON data back into an object:

const jsonData = ''; const data = JSON.parse(jsonData); console.log(data.name); // "John" console.log(data.age); // 30 console.log(data.email); // "john@example.com"

Using AJAX and JSON Together

When used together, AJAX and JSON can allow for powerful web applications that can communicate with a server in real time and update content dynamically. Here’s an example of how to use AJAX and JSON together to retrieve data from a server and update the content on a web page:

const xhr = new XMLHttpRequest(); xhr.open('GET', 'https://example.com/data'); xhr.onload = function() < if (xhr.status === 200) < const data = JSON.parse(xhr.responseText); const contentEl = document.getElementById('content'); contentEl.innerHTML = ''; data.forEach(function(item) < const listItem = document.createElement('li'); listItem.textContent = item.name; contentEl.appendChild(listItem); >); > >; xhr.send();

Conclusion

AJAX and JSON are two powerful technologies that can greatly enhance the functionality and user experience of web applications. By using AJAX to send and receive data asynchronously and JSON to encode and decode data, you can build modern, responsive web applications that communicate with servers in real time. By using the code examples and techniques described in this article, you’ll be able to implement AJAX and JSON in your own web applications with ease.