It depends on the party. I rarely, if ever go to an event without a friend. An entire mess of people is difficult and intimidating to meet and hangout with people while still having fun.
For me, unless it's my absolute closest friends, I hate going to parties. I'll try to hide and avoid talking to people because I never know what to say. If it's a company party, we try to leave after dinner or after the door prizes are given out.
If it's my close friends throwing the party, then it's really different and I'll talk and laugh and maybe even sing.
I generally avoid parties because I always seem to end up being cornered by a drunk or someone I really don't want to talk to while my partner disappears off somewhere so there's no hope of being rescued.
A little bit of both. I'm not a big party person to begin with, but usually I do a little bit of mingling with people I know and a little bit of chillin' on my own unless someone comes up to me. Having some sort of activity we can all do together really kinda helps or even just knowing someone else there that can introduce me to more people for me to socialize with because that just feels like the hardest step, honestly.
Most of the parties I get invited to, I tend to know many people there so I tend to mingle. There have been some occasions where I have been to parties with people I know but there have been people there I do not know, I tend to stick with those I know and speak when spoken to.