/**
 * Validates that a string is a valid web URL.
 *
 * @param urlStr - The string to validate.
 * @returns Whether the string is valid web URL or not.
 */
export declare function isURL(urlStr: any): boolean;
/**
 * Validates that a value is a number.
 *
 * @param value - The value to validate.
 * @returns Whether the value is a number or not.
 */
export declare function isNumber(value: any): value is number;
/**
 * Validates that a value is a string.
 *
 * @param value - The value to validate.
 * @returns Whether the value is a string or not.
 */
export declare function isString(value: any): value is string;
/**
 * Validates that a value is a non-empty string.
 *
 * @param value - The value to validate.
 * @returns Whether the value is a non-empty string or not.
 */
export declare function isNonEmptyString(value: any): value is string;
/**
   *
/**
 * Validates that a value is a nullable object.
 *
 * @param value - The value to validate.
 * @returns Whether the value is an object or not.
 */
export declare function isObject(value: any): boolean;
/**
 * Validates that a value is a non-null object.
 *
 * @param value - The value to validate.
 * @returns Whether the value is a non-null object or not.
 */
export declare function isNonNullObject<T>(value: T | null | undefined): value is T;
/**
 * Validates that a string is a valid Firebase Auth uid.
 *
 * @param uid - The string to validate.
 * @returns Whether the string is a valid Firebase Auth uid.
 */
export declare function isUid(uid: any): boolean;