@inlang/paraglide-js/dist/compiler/runtime/extract-locale-from-navigator.js

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import { isLocale } from "./is-locale.js";
/**
 * Negotiates a preferred language from navigator.languages.
 *
 * Use the function on the client to extract the locale
 * from the navigator.languages array.
 *
 * @example
 *   const locale = extractLocaleFromNavigator();
 *
 * @type {() => Locale | undefined}
 * @returns {string | undefined}
 */
export function extractLocaleFromNavigator() {
    if (!navigator?.languages?.length) {
        return undefined;
    }
    const languages = navigator.languages.map((lang) => ({
        fullTag: lang.toLowerCase(),
        baseTag: lang.split("-")[0]?.toLowerCase(),
    }));
    for (const lang of languages) {
        if (isLocale(lang.fullTag)) {
            return lang.fullTag;
        }
        else if (isLocale(lang.baseTag)) {
            return lang.baseTag;
        }
    }
    return undefined;
}