Since so many of the examples in this lesson involve anonymous callback functions, it seemed like a good time to delve into the subject of functional programming.

Mastering Javascript (or any language) requires that you really grok how things work at a deep level, and don't just copy-paste code without understanding it. Understanding what happens when you call a function, when you declare a function, what can be done with first-class function objects, and how closures work, will all help make you a much better programmer!