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What is middleware?

Middleware allows you to run code on a request before any routes are run. This is useful for things like authentication, header manipulation, and anything else that needs to happen before your routes are handled.

router.use()​

Middleware is attached by calling the router.use() method.

The example below shows how to use middleware to add a header to all requests:

router.use((req, res) => {
  res.set("x-powered-by", "expressly");
});

🚨 Unlike Express, middleware accept only two arguments, req and res. expressly does away with the next function; all errors are caught and handled by error middleware.

If you only want middleware to run on specific routes, you can pass a path to the middleware:

router.use("/api/(.*)", (req, res) => {
  console.log("Got a request to the API!");
});

expressly uses path-to-regexp to pattern-match routes. This means that your middleware mount paths can contain wildcards and even regular expressions.