[eigenket]

They index them with doubles, they do the same with loop variables. As long as your integer is less (in absolute value) than about 2^53 (because they have 53 bit mantisas) you can represent it exactly with a double. 2^53 is 2^(10*5+3) so even if you're indexing individual bytes that many indexes works until you need to index into an array with 8 petabytes of data in it, at which point you're probably not using javascript anymore.

Like many things in javascript it's a bit cursed but it does work.

[cryptonector]

Plus 53-bit indices exceed the amount of memory that many 64-bit architectures can address (x86_64 is 48 bits, ARM is either 48 or 52 bits).

[zokier]

x86-64 is 57 bits these days https://en.wikipedia.org/wiki/Intel_5-level_paging

[cryptonector]

Thanks for the correction! TIL.

[namibj]

Tbf, it's not commonly run because it increases TLB miss latency for rarely any benefit (why are you mmap-ing so much? How can you afford to keep that much data around...).