Marc Mintel
5397309103
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30 lines
839 B
Plaintext
30 lines
839 B
Plaintext
// Cache for Set conversions to avoid repeated array->Set conversions
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const availableLocalesSetCache = new WeakMap();
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/**
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* https://tc39.es/ecma402/#sec-bestavailablelocale
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* @param availableLocales
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* @param locale
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*/
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export function BestAvailableLocale(availableLocales, locale) {
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// Fast path: use Set for O(1) lookups instead of O(n) indexOf
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let availableSet = availableLocalesSetCache.get(availableLocales);
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if (!availableSet) {
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availableSet = new Set(availableLocales);
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availableLocalesSetCache.set(availableLocales, availableSet);
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}
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let candidate = locale;
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while (true) {
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if (availableSet.has(candidate)) {
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return candidate;
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}
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let pos = candidate.lastIndexOf("-");
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if (!~pos) {
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return undefined;
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}
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if (pos >= 2 && candidate[pos - 2] === "-") {
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pos -= 2;
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}
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candidate = candidate.slice(0, pos);
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}
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}
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