Perhaps not, but that doesn't necessarily imply that the use of CoffeeScript-only examples was a calculated move to reach the audience they wanted instead of whatever came to mind first. It's worth at least reminding them that JS examples might be more useful to more people and letting them decide consciously whether they care.

They use coffeescript's class inheritance. Here's the JS that compiles down to:

http://jashkenas.github.com/coffee-script/#classes

If they showed JS examples it would instantly turn everyone off. Trust me, you do NOT want to use this with JS.