Node.js & Libuv•Part 4: Express, Fastify, APIs & Middleware (36 - 50)
CORS and Preflight OPTIONS requests.
In Simple Words:
Preflight OPTIONS requests are sent by browsers for requests with non-simple methods (PUT, DELETE, PATCH) or custom headers (Authorization, Content-Type: application/json).
Safe configuration specifies explicit origin whitelist instead of wildcard *.
javascript
const cors = require('cors');
app.use(cors({
origin: ['https://myapp.com', 'https://admin.myapp.com'],
methods: ['GET', 'POST', 'PUT', 'DELETE'],
credentials: true
}));