Fetch API vs AJAX

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Both fetch and ajax (Asynchronous Javascript and XML) are used for making asynchronous HTTP requests, but they have some key differences in terms of usage, features and modern web development practices.

Fetch API

Overview

The fetch API is a modern interface that allows you to make network requests similar to XMLHttpRequest (XHR). However, it provides a more powerful and flexible feature set.

Key Features

• Promise-Based: fetch use Promises, making it easier to work with and handle asynchronous operations.
• Simpler Syntax: The syntax is more concise and readable compared to XMLHttpRequest.
• Streaming Responses: fetch allows you to access the body content while it’s still downloading, using the ReadableStream interface.
• Better Error Handling: With Promises, you can handle errors more elegantly using catch.

Example:

fetch('https://api.example.com/data')
  .then(response => {
    if (!response.ok) {
      throw new Error('Network response was not ok');
    }
    return response.json();
  })
  .then(data => {
    console.log(data);
  })
  .catch(error => {
    console.error('There was a problem with your fetch operation:', error);
  });

AJAX (Using XMLHttpRequest)

Overview

AJAX is a technique that use XMLHttpRequest to send and receive data asynchronously from a web server. It has been widely used in web development for a long time.

Key Features

• Widespread Support: XMLHttpRequest is supported all modern browsers.
• Complex Callbacks: Requires more setup with multiple callbacks for different stages of the request.
• More Control: Provides more granular control over the request, including progress events.
• Older API: The API is older and can be more cumbersome to use compared to modern alternative like fetch.

Example:

var xhr = new XMLHttpRequest();
xhr.open('GET', 'https://api.example.com/data', true);
xhr.onreadystatechange = function() {
  if (xhr.readyState === 4) {
    if (xhr.status === 200) {
      var data = JSON.parse(xhr.responseText);
      console.log(data);
    } else {
      console.error('There was a problem with your request:', xhr.statusText);
    }
  }
};
xhr.send();

Comparison Table

Feature	Fetch	AJAX (XMLHttpRequest)
API	Modern, promise-based	Older, callback-based
Syntax	Simpler, more concise	More complex, verbose
Error Handling	Easy with Promises (catch)	Requires manual handling with callbacks
Response Type	Can handle different types (Blob, Json)	Mostly handles text
Stream Handling	Supports streams	Limited steam support
Browser Support	Modern browsers	All browsers including older ones

When to Use Fetch

• Modern Applications: For new projects or modern web applications, the fetch API is recommended due to simplicity and improved feature set.
• Promise-Based Workflow: If you prefer or require a Promise-based approach for handling asynchronous operations.

When to use AJAX (XMLHttpRequest)

• Legacy Code: When maintaining or working with legacy systems that already use XMLHttpRequest.
• Greater Control: If you need fine-grained control over the HTTP request and response, include progress monitoring.

Written on November 17, 2024