perf: use indexed capture groups instead of named ones in parse()#283
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ordinary9843 wants to merge 1 commit intovercel:mainfrom
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perf: use indexed capture groups instead of named ones in parse()#283ordinary9843 wants to merge 1 commit intovercel:mainfrom
ordinary9843 wants to merge 1 commit intovercel:mainfrom
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Named capture groups are noticeably slower in V8 because the engine has to allocate a groups object and do property lookups. Switching back to indexed groups (match[1], match[2]) is a simple change that gets parse() back closer to v2 speed. Fixes vercel#273
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Noticed that v4 is quite a bit slower than v2 (#273), so I dug into why.
The regex in
parse()was changed to use named capture groups ((?<value>...),(?<unit>...)) when the TypeScript rewrite happened. Named capture groups are slower in V8 — the engine needs to allocate an extragroupsobject and do property lookups instead of just reading an array index. This is a known V8 thing and it adds up fast in hot paths.The fix is just switching back to indexed groups and reading
match[1]/match[2]. No behavior change, just faster.Numbers on my machine (Node 20, 500k iterations over 8 inputs):
That's roughly 66% faster for
parse(), which lines up with what was reported in #273.All 167 existing tests pass.