Question

How do I write this for loop in CoffeeScript?

for(i = cc.length – 2, i >= 0, i -= 2)

Answer 1

for i in [cc.length - 2..0] by -2
  ...

Compilation here. The by keyword isn’t very well-known, but it’s invaluable.

One caveat: You have to remember to do the range backward (upper..0). And you cannot iterate through an array backward with this approach:

for i in arr by -1  # infinite loop!