Working code for real-world HTTP patterns
These examples demonstrate practical HTTP patterns using vanilla JavaScript. Each example shows complete, working code you can study, copy, and adapt for your projects.
Client-side examples use the Fetch API and run in the browser. Server-side examples use Node.js built-in modules with no external dependencies.
Fetch data from an API with proper error handling and response parsing.
Send JSON data to a server with correct headers and body encoding.
Submit forms with FormData, URL encoding, and different content types.
Upload files with progress tracking and validation.
HTTP Basic Auth with base64-encoded credentials in the Authorization header.
Token-based auth with JWT, including storage, refresh, and expiration handling.
Handle HTTP error status codes gracefully with user-friendly messages.
Automatic retry for failed requests with exponential backoff strategy.
Set request timeouts and handle slow responses gracefully.
Cross-origin requests that don't trigger preflight checks.
Understanding OPTIONS preflight and Access-Control headers.
Sending cookies and auth headers with cross-origin requests.
Control browser caching behavior with proper Cache-Control directives.
Conditional requests with ETag and If-None-Match for cache validation.
Create a minimal HTTP server with Node.js built-in http module.
Route requests by method and path without external frameworks.
Build a RESTful JSON API with validation and proper status codes.