How do libraries/programming languages convert floats to strings

Question

This is a mystery that I was trying to figure out when I was 15, but I failed. I still don't know the answer.

Here's a naive and flawed solution (like some other failed attempts I've seen here on Stack Overflow):

const numberToString = number => {
  let result = '';
  let multiplier = Math.floor(Math.log10(number));
  while (number > 0) {
    const currentDigit = Math.floor(number / 10 ** multiplier);
    if (multiplier === -1) result += '.';
    result += `${currentDigit}`;
    number -= 10 ** multiplier * currentDigit;
    multiplier -= 1;
  }

  if (multiplier >= 0) {
    result += Array(multiplier + 1)
      .fill('0')
      .join('');
  }
  return result;
};

numberToString(0.3) //.29999999999999998010382707025852380980776467160900842259699366886095386217478302201335914442574948883370288946713085380211028267974348864228883494754227105763273602317743416839701366257194448416238466245093684421946526875873398794558223163136792877759774069929483218021428696258138483228158055137040848084556063610493291767

The language here is in Javascript, but the question is language agnostic. However, feel free to improve the existing code if it's possible.

If the way this works is language dependent, I would appreciate some insights how this might look in various programming languages, for example Javascript.

Answer 1

Libraries and programming languages convert floats to strings by formatting the float's binary representation into a human-readable string, often using specified precision rules to manage decimal places and rounding.