const process = (value) => value;
const value = Math.random();

const do1 = (x) => {
  return new Array(x).fill(null).reduce(process, value);
}

const do2 = (x) => {
  let updatedValue = value;

  for (let i = x; i > 0; i--) {
    updatedValue = process(updatedValue);
  }

  return updatedValue;
}