[vanderZwan]

Also, funny enough, this idea and variations of it look surprisingly easy to implement in JS itself using typed arrays. I won't any claims of impact on performance though...

You need a Float64Array for the values (plus a Uint32Array/Uint8Array using the same buffer to be able to manipulate the integer bits, which technically also requires knowledge of endianness since it's technically not in the JS spec and some funny mobile hardware still exists out there). Mocking a heap is easy enough: the "heap" can be a plain array, the "pointers" indices into the array. Using a Map<value, index> would you "intern" duplicate values (i.e. ensure doubles outside the unboxed range are only "heap" allocated once).