many young frum jews end up around nightlife at some point: bars, clubs, house parties, concerts. nobody claims it is a beis medrash, but what does halacha actually say?

1. is there an actual issur in being at a bar or a club, or is it a question of what happens there? if the problem is the content, which part is the problem: the drinking, the mixed dancing, the music, the crowd, the late hour?

2. halacha deals with each piece separately: yayin has its own rules, kol isha, mixed dancing, looking at what should not be looked at. is nightlife just the sum of those parts, or is there a broader idea about atmosphere that the poskim use, the place itself?

3. where is the line between a wedding or a bar mitzvah with music and drinking, which is a mitzvah atmosphere, and a club night? is it intent, setting, company?

4. and what about the person who goes and does nothing wrong, no drinking, no mixing, just friends and music? permitted, unwise, or forbidden?

bottom line: what does halacha say about nightlife and partying, and where exactly is the line?