How I can play java script game

Go here: http://htmlchess.sourceforge.net/demo/example.html or http://valil.com/chess/chess_include.html on your iPad.

Those JavaScript chess games work fine on the iPad. There are others if you Google for "Javascript chess game", but as PogoPossum said, you'll find better ones in the AppStore.

If you mean a java game (such as a website where you play chess), then you can't - iOS does not work with plug-ins like Java and Flash. Javascript does work on the iOS, but an interactive game is probably Java-based.

However, there are a number of chess apps in the App Store to choose from.