Adding JavaScript functions to enable chatting

Next, we need to add a few simple functions that will handle the chat messages received from the signaling server and that will enable the local users to send their own messages.

At the end of the existing start() function, we add two calls that define some basic functionality for the message_input bar.

The first step is to add an onkeydown event handler that checks each new character entered into the message_input bar, and if the latest one is a return, then it takes the full value of the message and sends it to the signaling server as a new_chat_message.

  document.getElementById("message_input").onkeydown =
    send_chat_message;

The second step is to add a simple onfocus event handler that clears the message_input bar so that you can start typing a new message. By default, we start with a simple hint that says Type here then hit enter... and we need to clear this as soon as you bring focus to the message_input bar.

  document.getElementById(...