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moment / luxon

⏱ A library for working with dates and times in JS
https://moment.github.io/luxon
MIT License
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[perf] isEnglish and supportsFastNumbers are slow - `new Intl.DateTimeFormat` #1428

Closed MonstraG closed 2 days ago

MonstraG commented 1 year ago

I'm profiling a calendar page which shows a bunch of events. I collect a profiling file and open it in https://www.speedscope.app, look at sandwich view, and see that isEnglish is the 3th slowest function (by self time) (and supportsFastNumbers is 5th): image

I take a look at isEnglish : https://github.com/moment/luxon/blob/07023283e74321c2080de9bb73070a3ffd2a7acc/src/impl/locale.js#L479-L485

As I'm working in Norwegian locale, I assume this returns false, but most importantly - creates new Intl.DateTimeFormat on every call.

I have not tried this yet, but I believe we can win some time if we cache Intl.DateTimeFormat (or avoid doing this check).

Same happens in supportsFastNumbers.

MonstraG commented 1 year ago

Looked at isEnglish a bit, and it seems that it's used to check whether to show a default built-in english locale or a proper Intl.

  1. This implementation of isEnglish fails for en-GB which is not considered english.
  2. Do we still need to ship this default locale at all?
icambron commented 1 year ago

Yeah, isEnglish really means isUSEnglish. We use it because it's much faster than using Intl, and many pre-built formats use it (e.g. parsing RFC2822 dates). The expensive part is checking if we can use it, and I think we can probably speed that up and/or make it less likely to be needed.

nodify-at commented 2 months ago

Hi team,

Is there a plan to improve this function? We've identified significant performance issues related to this function call, specifically with the line in Node.JS.

new Intl.DateTimeFormat(this.intl).resolvedOptions().locale.startsWith("en-us")

This part appears to consume a considerable amount of CPU, leading to noticeable performance degradation.

Any insights or plans for optimization would be greatly appreciated.

Thank you!