Performance rules (round 1)

[43081j]

We don't yet have any performance rules, so let's use this issue to track ideas.

We're looking for syntax replacements of {slow syntax} -> {fast syntax}.

NOTE, this isn't only about CPU perf, we should flag memory inefficient things too.

Suggestions

I'll update this list as we discuss.

• [...iter].map(mapper) to Array.from(iter, mapper)
  • Array.from only makes one copy whereas spread and map makes an intermediate array
• Array.from(iter) to [...iter]
• Array#forEach to for...of

[TomerAberbach]

nit: I think you meant to flip the things in the first bullet point :)

[43081j]

i've updated the list to make that clearer 👍

[ArnaudBarre]

If you go hard mode, any chain of filter+map should be done with for of + if