Version of javascript used by DOpus

What version of javascript is DOpus using?
I note that I cannot declare a variable using the "let" keyword, e.g.
let name = "David"; // Results in an error message

It seems that var is the only option. I understand that the "let" keyword was introduced in 2015 as part of Javascript ES6 (according to W3Schools). Is there a link to a reference document on the javascript language version used in DOpus?

DOpus does not have its own JavaScript engine, it uses Windows' builtin WSH/JScript, which hasn't been updated in some time and likely won't be anymore. It roughly corresponds to ES3, see here.
There are ways to overcome some of the limitations by transpiling.

Edit: For WSH documentation check out this awesome post.


Thanks cyilmaz. It has helped so much having the links (this awesome post) to the Microsoft JScript language reference documentation. The docs are quite concise, but just what I need as a learner JScript user. With my C# background it is pretty easy to whip up some pretty decent scripts in DOpus now. MUCH appreciated.