Express.js, or simply Express,
is a web application framework for Node.js, released as free
and open-source software under the MIT License. It is designed
for building web applications and APIs. It has been called
the de facto standard server framework for Node.js.
The original author, TJ Holowaychuk, described it as a
Sinatra-inspired server, meaning that it is relatively
minimal with many features available as plugins. Express is
the back-end component of the MEAN stack, together
with the MongoDB database software and AngularJS front-end framework.