freeCodeCamp/api-server/server/boot/z-not-found.js

import accepts from 'accepts';
import { getRedirectParams } from '../utils/redirection';

export default function fourOhFour(app) {
  app.all('*', function(req, res) {
    const accept = accepts(req);
    const type = accept.type('html', 'json', 'text');
    const { path } = req;
    const { origin } = getRedirectParams(req);

    if (type === 'html') {
      req.flash('danger', `We couldn't find path ${path}`);
      return res.redirectWithFlash(`${origin}/404`);
    }

    if (type === 'json') {
      return res.status('404').json({ error: 'path not found' });
    }

    res.setHeader('Content-Type', 'text/plain');
    return res.send('404 path not found');
  });
}