const msg = JSON.stringify({
  a: 123,
  b: true,
  c: "456"
})

const strencode = (str) => {
  let byteArray = [];
  for (let i = 0; i < str.length; i++) {
    let charCode = str.charCodeAt(i);
    if (charCode <= 0x7f) {
      byteArray.push(charCode);
    } else if (charCode <= 0x7ff) {
      byteArray.push(0xc0 | (charCode >> 6), 0x80 | (charCode & 0x3f));
    } else if (charCode <= 0xffff) {
      byteArray.push(0xe0 | (charCode >> 12), 0x80 | ((charCode & 0xfc0) >> 6), 0x80 | (charCode & 0x3f));
    } else {
      byteArray.push(0xf0 | (charCode >> 18), 0x80 | ((charCode & 0x3f000) >> 12), 0x80 | ((charCode & 0xfc0) >> 6), 0x80 | (charCode & 0x3f));
    }
  }
  return byteArray;
}

var arr = strencode(msg)
var buffer = Buffer.from(msg)

console.log(buffer)
for (let i = 0; i < arr.length; i++) {
  console.log(buffer[i], arr[i]);
}