Reverse string in JS

index.js

const isSupportSymbol = (symbolCode) => symbolCode === 55356 || (symbolCode >= 768 && symbolCode <= 879);
const reverse = (str) => {
  let res = '';
  let prevSymbol = null;
  for (const symbol of str) {
    if (isSupportSymbol(symbol.charCodeAt())) {
      res = `${prevSymbol}${symbol}${res}`;
      prevSymbol = null;
    } else if (prevSymbol == null) {
      prevSymbol = symbol;
    } else {
      res = `${prevSymbol}${res}`;
      prevSymbol = symbol;
    }
  }
  return res;
}

// test
reverse("😀👉🏿Ё👃🏽"); // "👃🏽Ё👉🏿😀"