MySortFn.js

function mySort(iterable, sortTestFn) {
  if (!Array.isArray(iterable) && typeof iterable !== 'string') return undefined;

  const join = (iterable) => {

    let str = '';

    for (let pos = 0, last = iterable.length - 1; pos <= last; pos++)
      str += iterable[pos];

    return str;
  };

  let referencePoint = 0,
      position = 0,
      tempArray = [...iterable],
      endOfIterable = tempArray.length - 1,
      typeOfReturn = typeof iterable;

  if (sortTestFn === undefined)
    sortTestFn = (a, b) =>
      typeof a === 'string' || typeof b === 'string' ? +(a > b) : a - b;

  while (referencePoint < endOfIterable) {
    if (sortTestFn(tempArray[position], tempArray[position + 1]) >= 1)  {
      [tempArray[position], tempArray[position + 1]] = [tempArray[position + 1], tempArray[position]];
      if (position > 0 && sortTestFn(tempArray[position - 1], tempArray[position]) >= 1) {
        position--;
        continue;
      }
    }
    position = ++referencePoint;
  }

  return typeOfReturn === 'string' ? join(tempArray) : tempArray;
}