What happens when you mouse over a menu, what happens when you type the wrong value in a form field, how long does a photo slideshow take to move from one image to the next? JavaScript is a programming language that you'll often hear it referred to as a scripting language, and sometimes you'll hear some software developers dismiss JavaScript as just being a scripting language. And what they mean by that is that JavaScript is intentionally limited. I can't write a desktop application in JavaScript the way I might do with C++ or Java or .NET or Objective-C.