What is Express.js middleware and how does it work?

What is Express.js middleware and how does it work?

Express.js middleware is a function that has access to the request, response, and next middleware function. It can modify the request and response objects, end the request-response cycle, and call the next middleware function in the stack.

Can you give me an example of middleware in Express.js?

Sure! A simple example is a logging middleware that logs the request method and URL. Here's how it looks:

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

How do I create my own middleware?

To create your own middleware, define a function that takes req, res, and next as parameters. Then, use app.use() to register it. For example:

function myMiddleware(req, res, next) {
    // Your logic here
    next();
}
app.use(myMiddleware);

What are some common use cases for middleware?

Common use cases for middleware include logging requests, handling authentication, parsing request bodies, and serving static files.