Node.js is an open source server-side framework built on top of the Google Chrome JavaScript Engine. The number of sites using NodeJS has increased by 84,000. It is one of the busiest cross-platform JavaScript runtimes. Node.js is an asynchronous, single-threaded, non-blocking I / O model that makes it lightweight and efficient. The Node.js package ecosystem, npm, is also the world's largest open source library ecosystem.