expressjsHow do I use middleware with Express.js?

Middleware functions are functions that have access to the request object (req), the response object (res), and the next middleware function in the application’s request-response cycle.

Express.js allows you to use middleware functions in the following way:

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

app.use(function (req, res, next) {
  console.log('Time:', Date.now());
  next();
});

app.get('/', function (req, res) {
  res.send('Hello World!');
});

app.listen(3000);

This example will log the current time before responding with ‘Hello World!’ when a request is made to the root URL.

Code explanation

1. const express = require('express'); - This imports the Express.js module.
2. const app = express(); - This creates an Express.js application.
3. app.use(function (req, res, next) { - This adds a middleware function to the Express.js application.
4. console.log('Time:', Date.now()); - This logs the current time.
5. next(); - This passes control to the next middleware function.
6. app.get('/', function (req, res) { - This adds a route handler for the root URL.
7. res.send('Hello World!'); - This sends a response with ‘Hello World!’.
8. app.listen(3000); - This starts the Express.js application on port 3000.

For more information on using middleware with Express.js, please see the official Express.js documentation.

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