Most appropriate when texting to save characters, JHTA can be used by the asker when following up to an unexpected, or unconventional, question of an associate/ friend; though, it may be used after most any question by the asker.
JHTA is not appropriate when communicating in work or professional email correspondence.
Lady texting: Hi! How r u?
Man texting: Gr8, thx. Hey, I'd really like 2 c u 2day. Do u hv plans? JHTA.