suddenly the cars headlights just flashed?

Hello my friend was driving along last night and suddenly the cars headlights just flashed we looked at the dash board and the battery light and the abs light had came on then after a couple of seconds the headlight just went off and couldn't be turned back on we left the car for a hour or two tried again still no lights we even tried changing the bulbs still nothing.. Someone has said to me that it could be the alternator is this so? Or can it be a quick fix?

P.S I didn't know the cars year as its my friends so I just guessed