gistfile1.js

> function fibonacciFactory() {
    var a=0, b=1;
    return function() {
      var next=a+b;
      a=b, b=next;
      return a;
    };
  };
  undefined
> next_fibonacci = fibonacciFactory();
  function () { var next=a+b; a=b, b=next; return a; }
> next_fibonacci();
  1
> next_fibonacci();
  1
> next_fibonacci();
  2
> next_fibonacci();
  3
> next_fibonacci();
  5
> next_fibonacci();
  8
> next_fibonacci();
  13