What is the difference between XMLHttpRequest and the fetch API?

The XMLHttpRequest and fetch API are both used for making HTTP requests in JavaScript, but they have some differences in terms of syntax, features, and how they handle data. Here are the key differences between them:

1. Syntax: The XMLHttpRequest object uses a more verbose and callback-based syntax, while the fetch API uses a promise-based syntax, which is generally considered more modern and easier to work with.
2. Promises: The fetch API returns a Promise by default, which allows for a more concise and readable code structure. On the other hand, XMLHttpRequest requires the use of callbacks to handle the asynchronous nature of the requests.
3. Browser Support: The XMLHttpRequest object has been supported by browsers for a long time, including older versions, making it widely compatible. In contrast, the fetch API is relatively newer and may not be supported in some older browsers without polyfills or transpilation.
4. Request/Response Objects: With XMLHttpRequest, you directly access the XMLHttpRequest object to handle request and response details. With the fetch API, you work with the Response object directly, which provides various methods and properties to handle response data.
5. Handling Errors: In XMLHttpRequest, you manually check the status and readyState properties to handle errors and monitor the progress of the request. With fetch, any non-2xx HTTP status code is considered an error and will cause the promise to be rejected. This simplifies error handling.
6. Request Abortion: The XMLHttpRequest object provides a built-in method called abort() to cancel an ongoing request. In contrast, the fetch API does not have a native way to cancel a request, although there are workarounds using third-party libraries or the AbortController interface.
7. Response Handling: fetch returns a Response object, which provides convenient methods like .json(), .text(), and .blob() to parse the response data. In XMLHttpRequest, you need to manually parse the response using methods like responseText or responseXML.

Overall, the fetch API offers a more modern and convenient way of making HTTP requests in JavaScript, with a simpler syntax and built-in Promises. However, XMLHttpRequest is still widely used and provides more extensive browser support, making it a suitable choice for older browsers or specific use cases.