@acastellon/cors

CORS filter for Node Express Application.

Install

npm install @acastellon/cors

Usage

const corsMod = require('@acastellon/cors')('./whitelist');
corsMod.enableCORS(app);

The whitelist file should contain one allowed origin per line (e.g. https://example.com). Origin check allows undefined (server-side) and matches exact.

Note: Whitelist is read synchronously at module load time.

API

enableCORS(app: ExpressApplication): void

Applies two middlewares:

1. Custom header setter (expose, allow headers for auth/cors, methods, credentials).
2. cors() from the 'cors' package, configured with origin whitelist check + credentials.

• Parameters: app - An express app (will call app.use twice).
• Side effects: Mutates the app by adding middleware. Reads whitelist file at construction time.
• Errors: Will call next(err) with 'Not allowed by CORS' for disallowed origins.

Minimal example (self-contained):

const express = require('express');
const corsMod = require('@acastellon/cors');
const fs = require('fs');
const path = require('path');

// Minimal whitelist file for demo
const wl = path.join(__dirname, 'whitelist.txt');
fs.writeFileSync(wl, 'https://example.com\nhttps://127.0.0.1\n');

const app = express();
const cors = corsMod(wl);

cors.enableCORS(app);

app.get('/api/test', (req, res) => res.json({ ok: true }));

app.listen(3000, () => console.log('Server with CORS started'));

License

MIT