What are some examples of middleware in Node.js?

What are some examples of middleware in Node.js?

Middleware in Node.js are functions that have access to the request, response, and the next middleware function. Examples include logging, authentication, and error handling.

Can you give me a specific example of a logging middleware?

Sure! A simple logging middleware could look like this:

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

This logs the HTTP method and URL of each request.

What about error handling middleware?

Error handling middleware is defined with four arguments. Here's an example:

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

This catches errors and sends a response.

How do I use these middleware in my application?

You can use middleware in your Express app by calling app.use(). For example:

const express = require('express');
const app = express();

app.use(logger);
app.use(errorHandler);

This applies the logger and error handler to all routes.