How to add Node Express Passport error handling?

To add Node Express Passport error handling, we use the middleware returned by passport.authenticate.

For instance, we write

app.post(
  "/login",
  passport.authenticate("local", {
    successRedirect: "/loggedin",
    failureRedirect: "/login",
    failureFlash: true,
  })
);

to call passport.authenticate to return the authentication middleware.

We use that as the argument of post to make it use Passport authentication.

We set the successRedirect and failureRedirect properties to set the redirect destination in both cases.