/**
 * Converts a string to CONSTANT_CASE.
 * @param {string} string_ - Input string
 * @returns {string} CONSTANT_CASE string
 * @example
 * constantCase("helloWorld"); // "HELLO_WORLD"
 * constantCase("Hello World"); // "HELLO_WORLD"
 */
export declare const constantCase: (string_: string) => string;