computePreferredLocaleList() — astro Function Reference

Source Code

packages/astro/src/i18n/utils.ts lines 115–144

export function computePreferredLocaleList(request: Request, locales: Locales): string[] {
	const acceptHeader = request.headers.get('Accept-Language');
	let result: string[] = [];
	if (acceptHeader) {
		const browserLocaleList = sortAndFilterLocales(parseLocale(acceptHeader), locales);

		// SAFETY: bang operator is safe because checked by the previous condition
		if (browserLocaleList.length === 1 && browserLocaleList.at(0)!.locale === '*') {
			return getAllCodes(locales);
		} else if (browserLocaleList.length > 0) {
			for (const browserLocale of browserLocaleList) {
				for (const loopLocale of locales) {
					if (typeof loopLocale === 'string') {
						if (normalizeTheLocale(loopLocale) === normalizeTheLocale(browserLocale.locale)) {
							result.push(loopLocale);
						}
					} else {
						for (const code of loopLocale.codes) {
							if (code === browserLocale.locale) {
								result.push(code);
							}
						}
					}
				}
			}
		}
	}

	return result;
}