You'll probably also end up learning a thing or two about JavaScript. Even now, 2 years after I first saw this, I'm seeing new things in it, and I've been doing JS for 20 years.
- Everything gets recomputed on any minor change.
- If a cell is referenced by N other cells, it will be recomputed N+1 times on every update. Worse, this can be exponential for A2=A1+A1, A3=A2+A2, which leads to A1 being recomputed 5 times. There's no sharing or memoization.
- Circular references are detected because they trigger a "too much recursion" exception.
- An impure cell "=Math.random()" will be observed with different values by its dependencies.
with (DATA) return eval(value.substring(1));
Anyway, I'm not aware of any JS feature which wouldn't be easily replicated in most other dynamic languages. JS was rather unlucky when it comes to language features - its development stalled for years, while in the same time Python, Perl, Ruby, PHP evolved quickly. JS only now gets features implemented in other langs many years ago.