Not Found & Method Not Allowed

Kaelum provides two handy middlewares to elegantly handle requests for non-existent routes (404) or incorrect methods (405).

405 Method Not Allowed

By default in Express, if a client requests POST /users but only GET /users is defined, the server returns a 404 Not Found. However, the correct REST response is 405 Method Not Allowed with an Allow header indicating the accepted methods.

Kaelum fixes this automatically via app.useMethodNotAllowed().

const app = require("kaelum")();

app.addRoute("/users", { get: (req, res) => res.json([]) });

// Must be registered BEFORE notFound() and useErrorHandler()
app.useMethodNotAllowed();

When a user triggers a 405, they receive:

{
  "error": "Method Not Allowed",
  "allowed": ["GET"],
  "path": "/users"
}

Custom 405 Handler

You can provide your own handler:

app.useMethodNotAllowed({
  handler: (req, res, allowedMethods) => {
    res.status(405).json({
      error: "You can't do that here",
      tryTheseInstead: allowedMethods
    });
  }
});

---

404 Not Found

If a route genuinely doesn’t exist, Kaelum can intercept the request before it falls through the void. Just add app.notFound() at the end of your route declarations.

app.addRoute("/hello", { get: (req, res) => res.send("Hello") });

// Register as a catch-all at the end
app.notFound();

Default response:

{
  "error": "Not Found",
  "path": "/unknown-url"
}

Custom 404 Handler

app.notFound((req, res) => {
  res.status(404).render("404-page", { url: req.path });
});

Note: The recommended order for the end of your app.js is:

1. Your custom routes (addRoute(), apiRoute())
2. app.useMethodNotAllowed()
3. app.notFound()
4. app.useErrorHandler()