Introduction to AJAX — What is AJAX? — Full form: Asynchronous JavaScript and XML — History and evolution — Traditional vs AJAX requests How AJAX Works — Client-server interaction model — Role of JavaScript, XMLHttpRequest, and the server — Asynchronous vs synchronous communication XMLHttpRequest Object — Creating an XMLHttpRequest — open(), send(), and responseText — readyState and status — GET vs POST with XMLHttpRequest AJAX with HTML and JavaScript — Loading data into a div — Form submission with AJAX — Updating DOM dynamically AJAX Using jQuery — $.ajax() method — $.get() and $.post() shortcuts — Success, error, and complete callbacks — Data formats: HTML, JSON, XML Handling JSON Data — What is JSON? — Receiving JSON from the server — Parsing JSON and rendering it — Sending JSON to server Error Handling in AJAX — HTTP error codes (404, 500, etc.) — Catching request timeouts — Using .fail() and .always() in jQuery Security Considerations — Cross-origin requests (CORS) — CSRF and XSS basics — Validating user input on the server AJAX and Forms — Submitting forms without reload — Validation feedback using AJAX — File upload with AJAX (FormData API) AJAX and REST APIs — Making API calls using AJAX — Displaying API data in UI — Pagination and filtering via API AJAX Polling and Long Polling — Auto-refresh content using polling — Server push using long polling — Pros and cons Fetch API (Modern Alternative) — Basics of Fetch API — Fetch vs XMLHttpRequest — Using fetch() with async/await Error Handling with Fetch — Catching fetch exceptions — HTTP status handling — JSON parsing errors AJAX Best Practices — Keeping requests efficient — Minimizing payloads — Caching responses Debugging AJAX Requests — Using browser DevTools — Network tab analysis — Console.log for debugging responses