/** Test if a value is a string. */
export declare const isString: (val: any) => boolean;
/** Test if a value is a number. */
export declare const isNumber: (val: any) => boolean;
/** Test if a value is a boolean. */
export declare const isBoolean: (val: any) => boolean;
/** Test if a value is a date. */
export declare const isDate: (val: any) => boolean;
/** Test if a value is a regex. */
export declare const isRegExp: (val: any) => boolean;
/** Test if a value is an error. */
export declare const isError: (val: any) => boolean;
/** Test if a value is a function. */
export declare const isFunction: (val: any) => boolean;
/** Test if a value is an arguments object. */
export declare const isArguments: (val: any) => boolean;
/** Test if a value is a plain object. */
export declare const isObject: (val: any) => boolean;
/** Test if a value is an array. */
export declare const isArray: (val: any) => boolean;
/** Test if a value is a stream. */
export declare function isStream(val: any): boolean;
/** Test if a value is a buffer. */
export declare function isBuffer(val: any): boolean;
/** Test if a value is empty. */
export declare function isEmpty(val: any): boolean;