Basic implementation of the Newton’s Method for narrowing in on a square root. NOTE: in Firefox the yield keyword doesn’t exist unless the script tag loading the function has a type of “text/javascript;version=1.7”. version must be 1.7 or higher.
The function fibonacci contains the keyword “yield” making the function a generator. When the function is called it returns an iterator. The first time the iterator’s next function is called the fibonacci function runs like normal until the yield keyword. Yield works just like return, returning the value specified. The next time “next” is called