function toByteArray(str) {

    const bytes = [];

    for (let i = 0; i < str.length; i++) {

      let charcode = str.charCodeAt(i);

      if (charcode < 0x80) {

        bytes.push(charcode);

      } else if (charcode < 0x800) {

        bytes.push(0xc0 | (charcode >> 6), 

                   0x80 | (charcode & 0x3f));

      } else if (charcode < 0xd800 || charcode >= 0xe000) {

        bytes.push(0xe0 | (charcode >> 12), 

                   0x80 | ((charcode >> 6) & 0x3f), 

                   0x80 | (charcode & 0x3f));

      } else {

        i++;

        charcode = 0x10000 + (((charcode & 0x3ff) << 10) |

                   (str.charCodeAt(i) & 0x3ff));

        bytes.push(0xf0 | (charcode >> 18), 

                   0x80 | ((charcode >> 12) & 0x3f), 

                   0x80 | ((charcode >> 6) & 0x3f), 

                   0x80 | (charcode & 0x3f));

      }

    }

    return bytes;

  }

​

​

​

function getBytes(str) {

  var utf8 = decodeURIComponent(str);

​

  var arr = [];

  for (var i = 0; i < utf8.length; i++) {

    arr.push(utf8.charCodeAt(i));

  }

  return arr;

};

​

console.log(getBytes('abcd§'));

console.log(toByteArray('abcd§'));