Node.js is an event-driven I/O server-side JavaScript environment based on V8. It is intended for writing scalable network programs such as web servers. It was created by Ryan Dahl in 2009, and its growth is sponsored by Joyent, which employs Dahl. Similar environments written in other programming languages include Twisted for Python, Perl Object Environment for Perl, libevent for C and EventMachine for Ruby. Unlike most JavaScript, it is not executed in a web browser, but is instead a form of server-side JavaScript. Node.js implements some CommonJS specifications. Node.js includes a REPL environment for interactive testing.