How can I know if user clicked the join meeting button on pre-join page

I want to add some extra things after user clicks on join meeting button, is there any way to know if user actually joined the meeting?

I am adding eventlistener in my js file after iframe is loaded but its not working.

var $joinBtn;
  onload: ()=>{
       $joinBtn = $('.jss35');
    }
$joinBtn.click(()=>{

}