How to get the current status of a javascript websocket connection

This is very straightforward : thereadyState property of the websocket contains the connection of the websocket at all times as specified in the WebSocket API

It will be one of the following values : CONNECTING OPEN CLOSING or CLOSED

A way to work around the error would be something like this :

if (yourWsObject.readyState !== WebSocket.CLOSED) {
   // Do your stuff...
}