Oh, I've figured out the problem. It turns out that changing a variable solved my problem.

From this:

  var decoded;
  for (const key of objectKeys) {
    if (originalText.includes(key)) {
      continue;
    } else {
      decoded = result.replaceAll(key, replaceObject[key])
    }
  }

To this:

  var decoded = result;
  for (const key of objectKeys) {
    if (originalText.includes(key)) {
      continue;
    } else {
      decoded = decoded.replaceAll(key, replaceObject[key])
    }
  }