Minesweeper
This is a run-of-the-mill minesweeper game, written in JavaScript. There are probably dozens of them out there. If you've never heard of the game and need instructions ... well ... Google it.
BTW, this was coded back in 1995 by a younger, less experienced, and less user-friendly version of my present self, so it's clunky, the code and development technique is sloppy, and instructions and error messages are dripping with vitriol. Chances are slim that I'll ever have the time or inclination to clean it up.