export declare const toString: () => string;
export declare const keys: {
    (o: object): string[];
    (o: {}): string[];
};
/**
 * 判断一个对象上的属性是不是非原型链上的属性
 * @param target
 * @param key
 */
export declare function hasOwn(target: object, key: string | number): boolean;
/**
 * 判断给定的值是不是原始类型
 */
export declare function isPrimitive(value: any): value is string | number | symbol | boolean;
/**
 * 判断给定的值是不是字符串
 */
export declare function isString(value: any): value is string;
/**
 * 判断给定的值是不是函数
 */
export declare function isFunction(value: any): value is Function;
/**
 * 判断给定的值是否是数值(严格判断是不是数值，数值字符串也不允许)
 * @param value
 */
export declare function isNumber(value: any): value is number;
/**
 * 判断给定的值是否是数值字符串(宽松的判断，数值或者数值字符串都是允许的)
 * @param value
 */
export declare function isNumberString(value: any): value is string;
/**
 * 判断给定的值是否是数组
 * @param value
 */
export declare function isArray(value: any): value is any[];
/**
 * Strict object type check. Only returns true
 * for plain JavaScript objects.
 */
export declare function isPlainObject(value: any): value is object;
/**
 * 判断一个值是null或者undefined
 * @param value
 */
export declare function isNullOrUndefined(value: any): boolean;