javascript.builtins.Intl.NumberFormat.NumberFormat - options.numberingSystem support listed incorrectly about browser-compat-data HOT 3 OPEN

There are two things wrong here:

1. numberingSystem should be an option of the constructor, not an option of format.
2. The only way to test whether Intl supports an option is to query resolvedOptions. Otherwise, the output may simply be due to lack of data.

Here's the output:

Therefore Firefox 75 does support numberingSystem. It's just that ar-EG data did not have the nu-latn combination.

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1. My apologies, I've corrected the screenshot in testing steps to match the actual steps used.
2. I see, that makes sense. Is there any way to detect which numberingSystems are supported beyond checking the resolved options after trying to apply them?
   Locale accessor numberingSystems returns ["arab"] on browsers that resolve the numberingSystem: "latn" option which seems to me like it contradicts the notes here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat/NumberFormat#numberingsystem
   Win/Chrome 125:
   

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@EdgarPl

Locale#numberingSystems returns the list of numbering systems that are commonly used in the locale. It doesn't necessarily mean the formatter only supports using those particular combinations (I could be wrong but that's my interpretation). When the doc says "For a list of supported numbering system types" it means to refer to the complete table for all values that are considered valid.

Is there any way to detect which numberingSystems are supported beyond checking the resolved options after trying to apply them?

I'm not sure either, as I'm not an expert on the CLDR data format. In fact, I believe it may be a non-issue in the latest browser version, because the data uses templates that gets filled in with any numbering system you want. For example, ar-EG with the hanidec (Positional decimal system using Chinese number ideographs as digits) numbering system is an obviously nonsensical combination, but Chrome formats it anyway:

new Intl.NumberFormat("ar-EG", { numberingSystem: "hanidec" }).format(1234)
// 一,二三四

resolvedOptions also doesn't indicate whether data is available. You may specify a non-sensical combination that doesn't have data, which will cause fallback when calling format, but this fallback won't be reflected by any other means.

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