Intl BestFitMatcher by using ICU LocaleMatcher

Category: JavaScript
Type: No developer-visible change
Status: In developer trial (Behind a flag) (Chrome 93)
Intent stage: Prepare to ship

Breaking change: No
Enterprise impact: None
Chromium flag: --harmony_intl_best_fit_matcher
Spec maturity: Unknown status
Web Platform Tests: Yes

WPT details: There are tests in test262 already testing the correctness of localeMatcher.

Summary

Use the ICU LocaleMatcher to implement the BestFitMatcher of ECMA402 in v8 JavaScript engine. ECMA402 defined the BestFitMatcher abstract operation to allow browser implementation to implement a better way to match locale data. UTS35 sec "4.4 Language Matching" details a data driven algorithm to use CLDR. ICU 67.1 (launched in April 2020) comes with an improved icu::LocaleMatcher API and implementation . This document shows how we implement v8's BestFitMatcher to use such API.

Standards & signals

Specification: https://tc39.es/ecma402/#sec-bestfitmatcher
Firefox: No signal
Safari: No signal
Web developers: No signals
Tracking bug: https://bugs.chromium.org/p/v8/issues/detail?id=7051

Ecosystem

Web Platform Tests: https://wpt.fyi/results/?q=intl-bestfitmatcher-by-using-icu-localematcher
Chrome Platform Showcase: https://chrome-platform-showcase.paulkinlan-ea.deno.net/features
GenDN reference: https://gendn.paulkinlan-ea.deno.net/features
chrome.dev demos search: https://www.google.com/search?q=site%3Achrome.dev+Intl%20BestFitMatcher%20by%20using%20ICU%20LocaleMatcher
MDN Web Docs: https://developer.mozilla.org/en-US/search?q=Intl%20BestFitMatcher%20by%20using%20ICU%20LocaleMatcher
Baseline status: https://webstatus.dev/?q=Intl%20BestFitMatcher%20by%20using%20ICU%20LocaleMatcher

Docs: https://docs.google.com/document/d/1cPGfiihn76yj2iAomKcspPFyLLcnk3WkCiqceBQPQyk/edit#

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