My goal was simply to see how feasible it was to write a "autoboxing" Promise subclass that could be used for async maps, the Service Worker API, etc. It turns out that the subclass is quite small and straightforward, although Promise.all() and Promise.race() won't work as-is on these "monadic" promises. The grisly details are mostly at https://github.com/domenic/promises-unwrapping/issues/95#issuecomment-35077555 (and in https://github.com/cscott/prfun/blob/monad-wip-1b/lib/index.js#L579-L599).
Anyway, I learned a lot, and I recommend the exercise. It turns out that enforcing a monadic semantics causes a lot of extra wrapping/unwrapping throughout the implementation (for example, an extra `.then` call per element in `Promise.all` and `Promise.race`). (Again, see the prfun monad-wip-1b branch for details.) I also implemented bluebird's `Promise.bind` using promise subclasses. I'm pretty happy with how subclasses work for the current Promise spec. (There are some corner cases, see https://github.com/domenic/promises-unwrapping/issues/94, but I didn't run into them in practice.) --scott _______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
