How do promises and error handling work in Express?

How do promises and error handling work in Express?

In Express, promises are used to handle asynchronous operations. You can return a promise from a route handler, and if it resolves, Express will automatically send the response. If it rejects, you can catch the error and pass it to the next middleware.

Can you give me an example of using promises in an Express route?

Sure! Here's a simple example:

app.get('/data', (req, res, next) => {
    getDataFromDatabase()
        .then(data => res.json(data))
        .catch(err => next(err));
});

In this example, getDataFromDatabase returns a promise.

What about error handling? How can I manage errors effectively?

You can manage errors by using middleware. Define an error-handling middleware function that takes four arguments: err, req, res, and next. This function will catch any errors passed to next() and send a response accordingly.

Can you show me how to set up an error-handling middleware?

Absolutely! Here's an example:

app.use((err, req, res, next) => {
    console.error(err.stack);
    res.status(500).send('Something broke!');
});

This middleware logs the error and sends a 500 response.