code: function containsToken(message, token, offset=0) {
    if (offset + token.length > message.length) {
      return false;
    }
  
    let index = offset;
    for (let i = 0; i < token.length; i++) {
      if (token[i] !== message[index++]) {
        return false;
      }
    }
    return true;
  }
docs: Checks whether a given token is contained by a message at a given offset.
  @param {Uint8Array} message message content
  @param {Uint8Array} token substring that should be present
  @param {Number} offset offset in message content from where search should start
  @returns {Boolean} whether message contains token at offset