import { OpenUrlOptions } from './typings/common';
export declare function _ensureFunction(fn: unknown): Function;
export declare function _openUrl(url: string, options?: OpenUrlOptions & {
    download?: string;
}): void;
/**
 * 是否是有效字符串
 * @param str
 * @returns
 */
export declare function _isString(str: unknown): boolean;