The fretboard calculator

In the eighties I wrote my first fretboard calculator, it was a "Lotus 123" file and I have been using it for more than thirty years.

Many years later I wrote it again in javascript to share it on my website, It's not an elegant script but  

it works!

Please feel free to save it on your pohne or even embed in your website (please quote me in that case).  I hope it could be useful for all Viol players and for makers of fretted instruments.