JavaScript - CORS & HTTP Patterns

Overview

Estimated time: 10–15 minutes

CORS (Cross-Origin Resource Sharing) controls access to resources across domains. Learn common HTTP patterns for robust web apps.

Learning Objectives

• Understand CORS and how browsers enforce it.
• Implement common HTTP request/response patterns.

Prerequisites

• JavaScript - Recursion & Composition

CORS Example

fetch('https://api.example.com/data', {
  mode: 'cors'
})
  .then(response => response.json())
  .then(data => console.log(data));

HTTP Patterns

// GET, POST, PUT, DELETE requests
fetch('/api/resource', { method: 'POST', body: JSON.stringify({ foo: 1 }) });

Common Pitfalls

• CORS errors are enforced by browsers and can't be bypassed from client-side code.

Summary

Understanding CORS and HTTP is essential for building secure, modern web applications.