5 знаков после запятой

const toFixed = (value, precision) => {
  const power = Math.pow(10, precision || 0);
  return String(Math.round(value * power) / power);
};

console.log(toFixed(0.123456789, 5)); // '0.12346'
console.log(toFixed(0.123456789, 2)); // '0.12'
console.log(toFixed(2.345, 2)); // '2.35'
console.log(toFixed(2.355, 2)); // '2.35'