What is Node.js?

Node.js is an execution environment that runs on top of the V8 JavaScript engine. Its base premise is that it is asynchronous and event-driven. This means that all the blocking operations, such as reading data from a file, can be handled in the background while the other parts of the application continue to do their work. When the data has finished loading, an event is emitted and whoever was waiting for the data can now execute and do the work.

From its inception, Node.js was designed to serve as an efficient backend for web applications. Because of that, it was widely adopted by companies of all sizes and industry types. Trello, LinkedIn, PayPal, and NASA are some of the companies that use Node.js in multiple parts of their technology stack.

But what is an execution environment? An execution environment provides basic functionality, such as APIs, for a programmer to write applications. Think about the browser, for example – it has the DOM, objects such...