Add Intl.NumberFormat formatRange

[sffc]

In the same vein as the Intl.DateTimeFormat.prototype.formatRange proposal, we should add a formatRange method to Intl.NumberFormat. We have clients who are requesting such a feature (google-internal link).

[zbraniecki]

Can you please make the request a bit more public? Motivation, use cases, reasons why it should be implemented by all browser engines and become part of the standard etc?

[sffc]

Example use cases:

1. What Android versions are supported? 15-24 (standard number range)
2. How much will your Uber ride cost in US? $10-$15 (currency range)
3. How much will your Uber ride cost in Switzerland? 10-15 CHF (currency range with longer symbol)
4. How long before your delivery arrives? 15-20 min (duration/unit range)

Why this belongs in the spec:

1. Number range formatting is locale-sensitive and hard for programmers to get right; it is not sufficient to simply concatenate two numbers with a "-" in between
2. A polyfill would have trouble implementing expectations like "$10-$15" repeating the currency symbol but "10-15 CHF" not repeating it; this is handled best in ICU internals
3. Brings parity with Intl.DateTimeFormat.prototype.formatRange, meeting programmer expectations

[zbraniecki]

Thank you!

this is handled best in ICU internals

Is that part of CLDR? How can we implement it in a non-ICU-specific fashion?

[sffc]

Thank you!

this is handled best in ICU internals

Is that part of CLDR? How can we implement it in a non-ICU-specific fashion?

Good question.

The CLDR spec does not specify the behavior of when to repeat the currency symbol or "collapse" it down. ICU currently performs a heuristic. I have an open bug to formalize ICU's heuristics into CLDR.

https://unicode-org.atlassian.net/browse/CLDR-11431

[sffc]

I plan to address this as part of my new proposal Intl.NumberFormat V3.

https://github.com/sffc/proposal-intl-numberformat-v3

[sffc]

Question about which options to add for range formatting:

tc39/proposal-intl-numberformat-v3#6