Examples of implementing iterative solutions for fib in js

Fib functions - iterative.

**Fib Explored.**

The following is based on some notes i've made while working through fib toy problems with others.



```
    /**

      Simple iterative Fib sequence generator

    */
    function fib_seq(n){

      var i = 1; 
      var s = [1,1];

      while ( ++i <= n ){ // How many times will this loop run? Hint: n + 1 (for zero) - 2, or n - 1 times.
       s[i] = s[ i-2 ] + s[ i-1 ];
      }

      return (n < 0) ? undefined : s; // if n was less than 0, we return undefined, otherwise the full sequence we builtup.

    }

    /**

      Simple iterative last Fib calculator

    */
    function last_fib( n ){

      var a,b,f,i;

      a = 0, b = f = i = 1;

      do {

        f = (( a = b ) + ( b = f ));  // Why does this work? hint: what do "()" mean in this expression.

      } while( ++i < n  );

      return n > 1 ? f : 1;

    }
```