Как создать функцию persistence()?

const persistence = (number, i = 0) => {
  const digits = number.toString().split('');
  const result = digits.reduce((acc, el) => acc * el);
 
  if(result > 9) {
    return persistence(result, ++i);
  }

  return ++i;
}

function persistence(num) {
    function multiply(n) {
        return n.reduce(function(a, b) {
            return a * b;
        });
    }

    var count = 0;

    while (num.toString().length > 1) {
        num = num.toString().split("");
        num = multiply(num);
        count++;
    }
    return count;
}

console.log(persistence(999));

let count = 0;

const persistence = num => {
	count = 0;
	const numbers = [...num.toString()];
	const result = numbers.reduce((n, next) => Number(n) * next, 1);
	if (num > 9) {
		persistence(result);
		count++;
	}
	return count;
};

persistence(999); // => 4