TServerPlayer.onNickChanges(str, str)

[fowlplay4]

You could do a check like this:

PHP Code:

//#CLIENTSIDE
function ChatBar.onAction() {
  if (ChatBar.text.starts("setnick")) {
    temp.new_nickname = ChatBar.text.substring("setnick".length());
    temp.old_nickname = player.nick;
  }
}