How do I create custom middleware in Express?

How do I create custom middleware in Express?

To create custom middleware in Express, you define a function that takes the request, response, and next parameters.

Can you give me an example of a simple logging middleware?

Sure! Here's a simple logging middleware:

function logger(req, res, next) {
    console.log(`${req.method} ${req.url}`);
    next();
}

You can use it by adding app.use(logger); in your Express app.

How do I handle errors in custom middleware?

You can handle errors by defining an error-handling middleware function with four parameters: err, req, res, next. Here's an example:

function errorHandler(err, req, res, next) {
    console.error(err);
    res.status(500).send('Something broke!');
}

Make sure to add it after all other middleware.

Can middleware be asynchronous?

Yes, middleware can be asynchronous! You can use async functions and await inside them. Just remember to call next() when you're done.