CoffeeScript’s existential operator

I was perusing CoffeeScript's documentation when I found a bit I'd overlooked: it's got an existential operator. The existential operator that allows you to access a variable but only if it exists. Without it, you'd write code like this:

if player and player.hat?
    hatColor = player.hat.color
    hatColor = undefined

With CoffeeScript's existential operator, you can avoid that.

hatColor = player?.hat?.color

This can shorten your code by a fair bit.