Set your Publisher ID in src/config/ads.ts to display live ads.
AJAX & Fetch Summary & Certification Exam
Earn your official AJAX & Asynchronous Web Specialist Certificate
Validate your expertise in asynchronous HTTP requests, XMLHttpRequest, Promises, Fetch API, FormData, AbortController, and CORS security.
Certification Review Checklist
Difference between full page reloads and dynamic asynchronous DOM updates.
Why fetch() does not reject on 404/500 and how to check response.ok.
Sending JSON payloads with method: "POST" and Content-Type headers.
Cancelling in-flight requests using AbortController and AbortSignal.timeout().
CORS headers, preflight OPTIONS requests, and Same-Origin Policy.
Set your Publisher ID in src/config/ads.ts to display live ads.
Test Yourself With Exercise
When using `fetch()`, what property should you check to verify that an HTTP request was successful with a 2xx status code?