To see an example of how lightweight Node.js can be, let's take a look at some sample code that starts up an HTTP server and sends Hello World to a browser:

var http = require('http');
http.createServer(function(req, res) {
    res.writeHead(200, { 'Content-Type': 'text/plain' });
    res.end('Hello World
');
}).listen(8080, 'localhost');
console.log('Server running at http://localhost:8080'); 

A few basic lines of code are all it takes to write a complete Node.js application. Running it with a simple Node.js app.js command will launch an HTTP server that is listening on port 8080. Point any browser to http://localhost:8080, and you will see the simple output Hello World on your screen! While this sample app doesn't actually do anything useful, it should give you a glimpse of the kind of power you will have while writing web applications using Node.js. If you don't have the initial Node.js development environment set up, we will discuss it in the next chapter.