digits_in_number.js

// hack
const f1 = (n) => String(n).length;

// log10
const f2 = (n) => Math.floor(Math.log10(n) + 1);

// recursive
const f3 = (n) => {
  if (n < 10) return 1;
  return 1 + fc(n / 10);
};

// while
const f4 = (n) => {
  if (n === 0) {
    return 1;
  }
  let result = 0;
  while (n > 0) {
    n = Math.trunc(n / 10);
    result++;
  }
  return result;
};