Listing of supported Math functions in Javascript

Thanks Jan, so I do a search for a reference manual of Javascript 6 (ECMAScript 6) and find this:
http://es6-features.org/#NumberTruncation

which lists the Math.trunc() as a valid built in function, however Max (8.5.3) does not support it. For example this simple code of:
function doit(hi)
{
post(Math.trunc(12.3));    
}

when sent the message of:
doit 1

yields the following error:
js: NOF_NxNR_js2.js: Javascript TypeError: Math.trunc is not a function, line 4
js: error calling function doit [NOF_NxNR_js2.js]

Indicatng the Math.trunc is not supported.

So perhaps Max developers decided to pick and choose which built-in functions to implement? (a bit of sarcasm ;) .

Yes I remember reading somewhere else that Max is supporting version 6 of Javascript.

So the original question still holds, what source of information are developers to use to program in javascript in the Max environment, not the Max/Live specific methods/properties (this is well documented in the Max reference manual) but the javascript language implementation.

So far the only method I have is to look at say:
https://developer.mozilla.org/en-US/docs/Web/JavaScript
pick a function I would like to use and cross my fingers that Max supports it.