Learning Redux

Express middleware

The HTTP library, express, allows us to extend the server by executing middleware on every request; for example, consider this:

const app = express()function middlewareFn (req, res, next) {  console.log('requested url:', req.originalUrl)  next()}app.use(middlewareFn)

The preceding middleware function logs the requested URL for each request, then continues with the rest of the request. If we want our middleware to reject the request, we can simply throw an error instead of calling next().