Amusing to native English speakers: the negative of this phrase is "Ne, ja!"
Doubly so for Aussies where "Nah, yeah" is an affirmative phrase.
Or for native Russian speakers, where the expression "Да нет (yes no)," means, "Not really."
Да нет наверное (lit. Yes no maybe) = probably not.
Possibly maybe... probably not...
I've heard both: "Yeah, no." and "No, yeah." in American English. The former usually being sarcastic. Acting like you're agreeing and then taking it back. "Wanna get some sun? - Yeah, no." The latter is indeed (Ja!) affirmative for us too.
Jes, ja! Nun kie estas mia okulvitro.
Why is "Yes, yes" not correct?
"Ja" en Esperanto ne signifas "yes," sed "indeed" aux "certainly."
"Ja" in Esperanto doesn't mean "yes," but "indeed" or "certainly." I guess you could consider it a false cognate to English.