node.js was built from scratch, in C, to resemble javascript syntax intentionally.
The only non-standard features of Node.js has been the module system (CommonJS), but even that will be ECMA standard as of next version.
(also, Node.js was built in C++ and JS)
The "that" in my sentence refers to "module system", not "CommonJS", but I agree my sentence was unclear.
From nodejs.org:
> Node.js® is a JavaScript runtime built on Chrome's V8 JavaScript engine.