It's very important for the one who build user-facing features on top of DOM and Web API to understand event propagation, bubbling, and capturing. Read on.
I don't have Mac, so doing the actual challenge might be frustrating. However, playing (copy-pasting) with Google Map API doesn't leave bad taste in my mouth. Read on.
Copying Array or Object can be tremendously confusing if we don't know that they are different from primitive typed values like string, boolean, or number. Read on.