Web
jQuery
I'm sure most of you can relate to that feeling you get when you learn about something that you're pretty sure everyone else already knows about. Something fundamental. I remember when I learned that I could test for nullable integers in C# by using hasValue. Or when I first learned that you could use array notation in JavaScript to dynamically access properties and methods. Sometimes we don't talk about these things. We sort of just look around to make sure no one was watching when we were the last to find out.