Considering that the Fibonacci sequence is exponential, and hence the Nth Fibonacci number contains O(n) digits (well, in any sane base at least), you cannot compute the Nth Fibonacci number in under O(n) time.
The javascript solution presented does everything in O(n) arithmetic operations, and the SICP way does it in O(ln(n)) arithmetic operations (actually, there are a lot of ways to do it in O(ln(n)) operations).
I mean, if we're going to screw around with the Os let's do it properly.