A simple server with Node.js

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\n');
}).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.

When to use Node.js

You may have heard of this proverb by an american psychologist, Abraham Maslow:

"If all you have is a hammer, everything looks like a nail!"

This makes a lot of sense in this context. Node.js is not a technology to depend for on all the application problems that you intend to solve, and if not chosen wisely, the decision to use it will backfire. Node.js is well suited for applications that are expected to handle a huge amount of concurrent connections. Also, it should be noted, it is most suited for applications where each incoming request requires very few CPU cycles. This means that if you intend to do computation-intensive tasks upon request, it will end up blocking the event loop, thereby impacting other requests concurrently processed by the web server. Node.js is well suited for real-time web applications, such as chat rooms, collaboration tools, online games, and so on. So, when deciding whether or not to use Node.js, we should analyze the application context seriously and figure out whether Node.js really suits the context of the application.

It is quite hard to debate over the use cases of Node.js in a detailed manner. However, the following Stack Overflow thread does this effectively, and I strongly recommend you to go through the answers on this post if you are more interested in the use cases of Node.js: http://stackoverflow.com/questions/5062614/how-to-decide-when-to-use-node-js.

As we have briefly gone through the concept and features of Node.js, now let's look into the NoSQL and MongoDB side.