The nightlife scene in Indonesia

This is a very complex question, much of the answer being down to where you are in Indonesia.

The basic rule is, the more nightlife with karaoke, alcohol, and 'entertainment' the more likely you are to be unsafe.
The hotspots in South Jakarta are frequented by the 'crowd', but also a great hunting ground for prostitutes, gold diggers, thieves, and pretty much every other unsavoury item you can think of.
That isn't to suggest expats out at night are in any serious danger, for the most part they aren't (save the odd mugging but the gangsters are getting shot by the cops of late so they're quieter than usual at the moment, especially the dead ones).
I'm assured the big tourist areas of Bali have pretty much the same issues.

On the far end of the scale, small towns have little to offer, many being pretty much empty by 10 at night. Most villages are dead after the last prayers.

Mid sized cities/large towns have the same issues as the larger places, just further down the scale.

Aceh is lively but it's all restaurants and coffee shops, the same pretty much applying to much of Kalimantan. Both are very safe with pretty much zero chance of anything bad happening to anyone.

I'll get shot down for my Jakarta comments and I'll admit bias because I don't care for the party scene. Too many years watching drunks whilst working as a DJ colours your opinion.

Pretty much agree with the first comment but with the added hookers/ prostitution in 99% of towns and cities across Asia / world Indonesia being no exception

Depending on your preference and obviously your location they are plenty of places to eat and or drink

As a fuller picture it is probably one of the safer places to be (Indonesia) but on the flip side it's on par with many places for scams and over changing purely for being a foreigner
It's no secret here (in fact common knowledge) that many police dressed as civilians frequent these places on duty and off duty for various reasons

Eating here is big every night till around 9/10pm all restaurants etc and street stalls are full
Bars are steady every night as the oil and gas industry typically dictates that scene, weekends 1000s visit for golf, prostitution, clubs, just get drunk, shopping for trashy stuff but the biggest one is the women for the salons, you would think it's the January sales in the UK

I'm out most Fridays after work till whatever time early or late and the last Sunday of the month (mum and toddlers pool party's)
9/10 Saturday and Sundays is with the kids or a weekend in sentosa or some other place in Singapore (got to do my marks and Spencer shop)
Almost always I visit the same bars, owners of several are my neighbors and friends so they all but tell the scammers and hookers to stay away, 1. I'm married, 2. I'm a friend 3. The wife would cut something off I'm not willing to lose

It's here if you want it, you'll get robbed or scammed if you act stupid and flaunt it, you'll get a good kicking for being disrespectful so it's no different from home
Act all normal like you would back home with family and friends you'll be fine
I use the same driver I have done for over 4 years as do several of my friends and he's very trustworthy

Food, food, food.
Apart from the popular street stalls, there are thousands of clusters of stalls set up in a square with tables in the middle.
These are very popular with night eaters and they're generally very cheap.
Some of these are getting very posh, sporting covered seating areas with lighting, commonly a large TV or projector, and real toilet blocks.
Even smaller towns are getting these foody entertainment areas.