As I understand it Salesforce CommerceCloud uses Rhino JavaScript, but sadly I cannot find what version it is, which is important for understanding compatibility. Is there any documentation that describes this, and/or is there a way to output the JavaScript engine version?
Rhino 1.7R5
I was pointed to an answer on GitHub SFCC community docs FAQ (requires login), which cited an official post on a forum from 2016:
... the supported language dialect Demandware Javascript is Rhino Javascript (currently Rhino release 1.7R5) ...