What is XMLHttpRequest? Complete Guide to XHR in JavaScript
Blog post from Postman
XMLHttpRequest (XHR) is a core JavaScript API that enables asynchronous communication between web pages and servers, forming the backbone of interactive web experiences and AJAX (Asynchronous JavaScript and XML) applications. It allows web pages to request and update data without reloading, handling formats like JSON, HTML, and XML. This guide explains XHR's request-response model, highlighting key stages such as creating an XHR object, configuring requests, setting up event handlers, and processing responses, with examples of GET and POST requests. Additionally, it emphasizes error handling, testing with Postman, and best practices such as setting appropriate timeouts, specifying content types, and avoiding synchronous requests. While modern browsers favor the Fetch API for its cleaner, promise-based syntax, understanding XHR is crucial for maintaining legacy systems, ensuring precise progress tracking, and supporting older browsers. The text also discusses transitioning to Fetch when building new applications and the importance of testing API requests in Postman for efficient troubleshooting and code validation.
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