Question

Can anyone explain why this won’t work? I am just running this off of the CoffeeScript page’s “Try Coffeescript now” thing and my Chrome console logs the “nope” as you’ll see below

x = true
foo = (x = x) ->
  console.log if x then "works" else "nope"
foo() # "nope"

If I had changed the x = true to y = true and ( x = x) to ( x = y ) in the argument definition

Thanks a million!

Answer 1

Seeing how the function is compiled makes the problem obvious:

  foo = function(x) {
    if (x == null) x = x;
    return console.log(x ? "works" : "nope");
  };

As you can see, if the x argument is null, x is assigned to it. So it’s still null.

So, renaming the x variable to y fixes the problem:

y = true
foo = (x = y) ->
  console.log if x then "works" else "nope"
foo() # "nope"