@gravityforms/utils/src/data/get-valid-locale.js

JavaScript utilities for Gravity Forms development.

/**
 * @function getValidLocale
 * @description Returns a valid locale string.
 *
 * @since 4.0.8
 *
 * @param {string} locale   The locale string to validate.
 * @param {string} fallback The fallback locale string.
 *
 * @return {string} The valid locale string.
 */
const getValidLocale = ( locale = '', fallback = 'en-US' ) => {
	try {
		if ( ! locale ) {
			// Throw to enter the catch block for consistent handling.
			throw new Error( 'Locale not provided' );
		}
		// The Intl.Locale constructor validates the structural correctness of the locale string.
		const localeObj = new Intl.Locale( locale );

		// We then use Intl.DateTimeFormat to check for runtime support.
		const resolvedLocale = new Intl.DateTimeFormat( locale ).resolvedOptions().locale;

		// If the resolved language differs from the requested language, it indicates the
		// environment has fallen back to a default locale because the requested one is unsupported.
		if ( new Intl.Locale( resolvedLocale ).language !== localeObj.language ) {
			throw new Error( `Unsupported locale: ${ locale }` );
		}

		return resolvedLocale;
	} catch ( e ) {
		// All errors (invalid structure, unsupported, or empty) are handled here.
		console.warn( `The locale ${ locale } is invalid or unsupported, falling back to ${ fallback }.` );
		return fallback;
	}
};

export default getValidLocale;