const array = [3, 'a', 'a', 'a', 2, 3, 'a', 3, 'a', 2, 4, 9, 3];

const getMostFrequentValue = array => {
  const countAllValues = array.reduce((acc, curr) => {
    if (curr in acc) {
      return { ...acc, [curr]: acc[curr] + 1 }
    }

    return { ...acc, [curr]: 1 }
  }, {})

  let matushkuEbalReduca = 0;
  let forRulitSuka = null;

  for (const value in countAllValues) {
    console.log(countAllValues[value], value);
    if (countAllValues[value] > x) {
      x = countAllValues[value];
      res = `key ${value} times ${countAllValues[value]}`
    }
  }
  return forRulitSuka;
}

console.log(getMostFrequentValue([0, 0, 1]));