Nightlife in the mountains is up to you. In the popular Lake Basin and some other areas - ie Glacier Lake - campfires are prohibited. You can still sit our awhile resting tired bones while looking out over the landscape as it changes color, minute-to-minute, with the sunset. Your libation is limited only by what you can carry;-\
Dress Code: After the sun goes down, be prepared for the temperatures to drop fast!
To be honest, there's only a couple of places to go at night in Joseph -- The Hydrant Tavern, which has a pool table and where my daughter and her friends like to gather when she's home for karaoke (update: at least before she became a mother in Oct. '04) ; and the Stubborn Mule, which includes a restaurant and decent food, a sports bar and I think also does karaoke. There are occasionally live bands.
The most historic tavern/restaurant/upstairs apartment, the Gold Room and Cowboy Bar, has been closed for several years (except for an ill-fated opening of a few months last year), so if any one wants to own a bar in Joseph ...... (update: it is now a real estate office with commercial space to rent).
During Chief Joseph Days there's also a live band dance at the Thunder Room at the rodeo grounds, and other times there's an occasional live band dance at the community center, like during the Oregon Mt. Cruise in June.
Dress Code: Very casual. I don't know that they ever have had a customer wearing a suit or tie. (Except for the night of my daughter's wedding when everyone in the wedding party, including the bride and groom, went out on the town after the reception. Tuxes were then the norm.)