Difference Between AJAX And Fetch API

Last Updated : 01 Jul, 2024

AJAX (Asynchronous JavaScript and XML) and Fetch API are both powerful tools used in modern web development for making asynchronous HTTP requests. Each has its strengths and specific use cases that developers should consider when deciding which to use. In this article, we will see the main differences between AJAX and Fetch API.

AJAX

AJAX is a technique used in web development to send and receive data from a server asynchronously without interfering with the display and behaviour of the existing page. It enables updating parts of a web page with new data without reloading the entire page. Originally, AJAX relied on the XMLHttpRequest (XHR) object to make requests and handle responses. It has been a fundamental part of dynamic and interactive web applications for many years.

Advantages of Ajax:

Allows data to be exchanged with the server asynchronously without reloading the entire page.
Enables dynamic content updates, providing a smoother and faster user experience.
AJAX has been supported across browsers for a long time, making it a reliable choice for cross-browser compatibility.
Supports complex requests and responses, custom headers, and handling of various data formats like XML, JSON, etc.

Disadvantages of Ajax:

Managing asynchronous operations with callbacks can lead to callback hell, making code difficult to maintain and debug.
Cross-site scripting and cross-site request forgery vulnerabilities need to be carefully managed, especially when handling sensitive data.
AJAX requests can impact performance if not managed efficiently, especially with multiple concurrent requests.
Although widely supported, older versions of Internet Explorer may require specific handling and workarounds.

Pseudo Code:

var xhr = new XMLHttpRequest();

xhr.open('GET', '/data_endpoint', true);

xhr.onreadystatechange = function() {
    if (xhr.readyState === XMLHttpRequest.DONE) {
        if (xhr.status === 200) {
            // Request was successful, handle the response
            console.log(xhr.responseText);
        } else {
            console.error('Error occurred: ' + xhr.status);
        }
    }
};

// Send the request
xhr.send();

Fetch API

Fetch API is a modern JavaScript interface for fetching resources across the network. It provides a more powerful and flexible way to make HTTP requests compared to the older XMLHttpRequest. Fetch API uses Promises to handle responses, allowing for cleaner and more readable asynchronous code. It simplifies the process of fetching resources like JSON data, images, or other files from a server, and it supports all standard HTTP methods (GET, POST, PUT, DELETE, etc.).

Advantages:

Provides a cleaner and more modern interface using Promises, leading to more readable and maintainable code.
Automatically parses JSON responses, simplifying the handling of common data formats.
Offers a more straightforward syntax compared to XHR, reducing boilerplate code.
Provides more consistent and robust error handling mechanisms, including built-in support for handling network errors.

Disadvantages:

Fetch API is not supported in older browsers (e.g., Internet Explorer versions prior to 11) without polyfills or additional libraries.
Fetch API does not have built-in support for timeout handling, requiring manual implementation.
Fetch API may require more effort for handling specific scenarios like progress tracking or sending/receiving non-JSON data.
Transitioning from XHR to Fetch API may require developers to learn new concepts like Promises if they are not already familiar.

Pseudo Code:

fetch('/data_endpoint')
    .then(response => {
        if (!response.ok) {
            throw new Error('Network response was not ok');
        }
        return response.json(); 
    })
    .then(data => {
        console.log(data);
    })
    .catch(error => {
        // Handle errors
        console.error('Fetch Error :-S', error);
    });

Difference between AJAX vs Fetch API:

Feature	Ajax	Fetch API
Definition	Asynchronous JavaScript and XML, a technique for creating asynchronous web applications.	Modern JavaScript API for making network requests.
Standardization	Not a formal standard, but widely used.	Part of the standard JavaScript API.
Syntax	Verbose and complex.	Simplified and cleaner syntax.
Promises	Requires libraries (e.g., jQuery) for promises.	Built-in support for promises.
Response Handling	Uses callbacks for handling responses.	Uses promises and async/await for responses.
Error Handling	Complex, with callbacks for error handling	Simplified, with .catch() for errors.
Support	Broad browser support, including older browsers.	Modern browsers, but polyfills available for older ones.
CORS	Requires additional configuration for cross-origin requests.	Handles CORS more seamlessly with proper headers.
Chaining Requests	Difficult to chain multiple requests.	Easy to chain requests with promises.

Conclusion

AJAX, leveraging XMLHttpRequest, is a traditional method for asynchronous data fetching in web applications, offering compatibility with older browsers but featuring more complex syntax. On the other hand, the Fetch API, introduced with ES6, provides a streamlined promise-based approach with built-in JSON support, enhancing readability and ease of use in modern browsers.

1. Can I use the Fetch API in older browsers?

The Fetch API is supported in modern browsers. For older browsers, you may need to use polyfills to ensure compatibility.

2. How does the Fetch API improve over Ajax?

The Fetch API simplifies the process of making network requests with a cleaner, more readable syntax. It uses promises for easier asynchronous operations, and it handles JSON responses natively.

3. Which one should I use, Ajax or Fetch API?

For new projects, it's recommended to use the Fetch API due to its modern features and simplicity. However, if you need to support very old browsers or are maintaining legacy code, Ajax might still be necessary.

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Article Tags :

Difference Between AJAX And Fetch API

AJAX

Advantages of Ajax:

Disadvantages of Ajax:

Pseudo Code:

Fetch API

Advantages:

Disadvantages:

Pseudo Code:

Difference between AJAX vs Fetch API:

Conclusion

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