How do i make it so that if you press a button and then a different button you will get something written on your screen?

Okey, so it may sound confusing, but this is what i want to do:

You have 4 buttons. Button A, button B, button C, and button D. If you press button B and button C it will say for example "hi". Then if you press B and A it will say "Hello". So different button combinations will give you different "results" i guess.

Anyone have an idea on how i could do this? I do not have much experience with java script so it would be higly appreciated if someone would help me. :-)