Building a Simple Web Application in Node.js: Hello World Example

Here's an example of a simple web application in Node.js that prints "Hello World!!":

const http = require('http');

const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.end('Hello World!!\n');
});

const port = 3000;
server.listen(port, () => {
  console.log(`Server running at http://localhost:${port}/`);
});

To run this code:

1. Make sure you have Node.js installed on your machine.
2. Create a new file called app.js and copy the above code into it.
3. Open your terminal and navigate to the directory where app.js is located.
4. Run the following command to start the server:

node app.js

5. You should see the message Server running at http://localhost:3000/ printed in the terminal.
6. Open your web browser and visit http://localhost:3000/. You should see "Hello World!!" displayed on the page.

This code sets up a basic HTTP server using the Node.js http module. The server listens on port 3000 and responds with "Hello World!!" for any incoming requests. The response has a status code of 200 (OK) and a Content-Type header set to text/plain.