What is the difference between session Id obtained from _generateSessionId() and the one obtained by parsing sockjs._transport._url?

There are two types of session Id visible in sockjs One obtained by calling the function _generateSessionId directly on SockJs object returned here
const sockJs = new SockJs('http://example.com/ws/api')

and another session Id visible when printing the entire sockJs object in console and parsing sockJs._transport._url object inside it which gives us something like this

ws://example.com/ws/api/333/zf2j9qxe/websocket

according to my reading, zf2j9qxe is the actual session Id which is different than the one returned from the function call previously

Which one is the real one?