It uses prefix-free, which is a script, in order to be cleaner-looking code. As the author says: > The JS used is prefixfree - just to make the length and size

It uses prefix-free, which is a script, in order to be cleaner-looking code. As the author says: > The JS used is prefixfree - just to make the length and size of the tutorial short and easy. No images or JS are used in the stopwatch logic/display. It would be trivial to make a new -really- JS free version, but it wouldn't be so easy to understand. It could be non-js in production, it just isn't for teaching purposes, so I am happy to accept it as a 'non-js' stopwatch.