function toHexString(byteArray) {

  return Array.from(byteArray, function(byte) {

    return ('0' + (byte & 0xFF).toString(16)).slice(-2);

  }).join('')

}

​

function hexToByteArray(hexString) {

  const byteString = hexString.match(/.{1,2}/g); // Split the hex string into pairs of characters

  const byteArray = byteString.map(byte => parseInt(byte, 16)); // Convert each pair to a decimal value

  return byteArray;

}

​

// Example usage:

const hexString = "5468697320697320612068657820737472696e67";

const byteArray = hexToByteArray(hexString);

console.log(byteArray);