/**
 * Determines if a string is a valid JavaScript identifier.
 *
 * @param {string} str - The string to check.
 * @param {object} [options] - The options for checking.
 * @param {boolean} [options.allowAsync=false] - Whether to support 'async ' prefix.
 * @returns {boolean} - True if the string is a valid identifier, false otherwise.
 */
export function isIdentifier(str: string, options?: {
    allowAsync?: boolean;
}): boolean;
export default isIdentifier;