We use Node JS to build backend services for web applications (also referred to as Application Programming Interfaces or APIs). Node JS is ideal for building highly scalable, data-intensive, real-time backend services that power client applications.
Some major corporations that use Node JS in their stack include Netflix, Paypal, NASA, eBay among numerous others.
Below is the code to a simple Hello World program that runs on port 3000 on your localhost server.
When Node.js performs an I/O operation, like reading from the network, accessing a database or the filesystem, instead of blocking the thread and wasting CPU cycles waiting, Node.js will resume the operations when the response comes back.
This allows Node.js to handle thousands of concurrent connections with a single server without introducing the burden of managing thread concurrency which could be a significant source of bugs.