/**
 * A function which can be used as a function parameter default which throws an error
 * if the parameter is undefined
 *
 * @param {string} [varname] - name of the variable for the output
 * @throws {Error}
 */
function isRequired (varname) {
    const message = varname
        ? `missing parameter '${varname}'`
        : 'missing parameter';

    throw Error(message);
}

module.exports = isRequired;