expressjsHow do I use Express.js middleware in my web application?

Express.js middleware is a powerful and useful tool for creating web applications. It is a layer of code that sits between the application and the server, and it is used to perform a variety of tasks, such as logging requests, validating user input, and handling errors. Middleware can be used to add functionality to your application, and it can be used to modify the request and response objects.

To use Express.js middleware in your web application, you need to register the middleware with the Express application. This can be done with the app.use() method. For example:

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

// Register middleware
app.use(function(req, res, next) {
  // Do something
  next();
});

// Start listening
app.listen(3000);

The app.use() method takes a callback function which is called with the request and response objects, and a next function. Inside the callback, you can perform any logic you need, and then call the next() function to continue the request-response cycle.

In addition to registering the middleware with the Express application, you can also specify the order in which the middleware is called. This is done by passing an optional path argument to the app.use() method. For example:

// Register middleware
app.use('/api', function(req, res, next) {
  // Do something
  next();
});

In this example, the middleware will only be called for requests that match the /api path.

Express.js middleware is a powerful and useful tool for creating web applications. By registering the middleware with the Express application, and specifying the order in which the middleware is called, you can extend the functionality of your application and modify the request and response objects.

Helpful links

• Express.js Middleware
• Express.js API Reference

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