How do I use middleware in Express?

How do I use middleware in Express?

Middleware in Express is a function that has access to the request, response, and next middleware function. You can use it to modify the request and response objects, end the request-response cycle, or call the next middleware in the stack.

Can you give me an example of a simple middleware?

Sure! Here's a simple logging middleware:

app.use((req, res, next) => {
    console.log(`${req.method} ${req.url}`);
    next();
});

This logs the HTTP method and URL of each request.

How do I apply multiple middleware functions?

You can apply multiple middleware functions by passing them as arguments to app.use(). For example:

app.use(middleware1);
app.use(middleware2);

They will be executed in the order they are defined.

What if I want to use middleware for specific routes?

You can specify middleware for specific routes by passing it as a second argument to the route handler. For example:

app.get('/user', middlewareFunction, (req, res) => {
    res.send('User data');
});

This applies middlewareFunction only to the /user route.