js/Object.keys. I'd recommend checking out all the API of the most common built-in JS types. Or, if by "see" you mean literal visual inspection, then just js/console.log, assuming you have something akin to a browser's JS console.

do you have a reference you recommend for this @U2FRKM4TW?

MDN, 100%: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects You don't have to know everything by heart, but you should be aware of what exists.