I think many will say Javascript and something else. Working in any web stack, you are likely to use Javascript (almost) on a daily basis. And much less likely

I think many will say Javascript and something else. Working in any web stack, you are likely to use Javascript (almost) on a daily basis. And much less likely to use Javascript or Javascript-based technology on the back end. I think I would also add SQL, for the "not no-SQL" backing store. This is a funny beast: a programming language which (arguably) has not originally been intended to be used as a programming language, but often is. (I use C# for the middle tier, but it could be anything depending on the stack.)