/**
 * Data and Structure types
 * See also: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures
 */
export declare function isNull(x: unknown): x is null;
export declare function isUndefined(x: unknown): x is undefined;
export declare function isBoolean(x: unknown): x is boolean;
export declare function isNumber(x: unknown): x is number;
export declare function isString(x: unknown): x is string;
export declare function isBigInt(x: unknown): x is bigint;
export declare function isSymbol(x: unknown): x is symbol;
export declare function isNotNullOrUndefined<T>(x: T): x is NonNullable<T>;
export declare function isObject(x: unknown): x is object;