Node.js is an open-source, cross-platform, back-end
JavaScript runtime environment that runs on a JavaScript Engine
(i.e. V8 engine) and executes JavaScript code outside a web
browser, which was designed to build scalable network applications.
Node.js lets developers use JavaScript to write command line tools and
for server-side scripting-running scripts server-side to produce dynamic
web page content before the page is sent to the user's web browser.
Consequently, Node.js represents a "JavaScript everywhere"
paradigm,unifying web-application development around a single
programming language, rather than different languages for server-side
and client-side scripts.