Don't know why this comment is downvoted, because he has a point. Writing actual code on whiteboard is different, unless it's pseudocode without any syntax rules and standard libraries.

I'm not a newbie (like, 15 years coding). But I haven't even bothered to properly remember standard libraries peculiarities - since they're different across the languages anyway, and with modern software stacks (that are quite diverse) it's not unusual to write Python but do some C or C++ one day (speed-ups), detour to JavaScript, try out Elm, then have a day patching some Go code that an useful tool is written in, then go learning some Elixir. Is it strpos(substring, string) or strpos(string, substring)? What does base64.encode(blob) returns, again, ASCII bytes blob or a text string? Which module/header file contains/exports that symbol? Maybe I'm doing it all wrong but I honestly never remember such details that for longer than a week or another - a proper tooling always hints those kind of things to me, so I don't even recognize I tend to forget them.

On a whiteboard, I'd have some awkward moments.