This is true for the most part, but there's a subtle edge case. Within a nested function, variables used in loops will redeclare within the inner function: -

This is true for the most part, but there's a subtle edge case. Within a nested function, variables used in loops will redeclare within the inner function: -> outerVar = "outer" -> # this will output "undefined" # as CoffeeScript has redeclared it for the loop: console.log outerVar 0 for outerVar in [0]