[zeckalpha]

> I need it.

Need is a strong word.

[callahad]

In this case, "need" refers to the "if (x === undefined) { x = y }" pattern. Which is absolutely a need when implementing functions with variable arity.

If I need that pattern, I'd rather write it declaratively than imperatively. :)

[zeckalpha]

Variable arity is exactly the thing to which I refer. It isn't needed.