CloseEvent

gistfile1.txt

<script>
try{
	var websocket = new WebSocket("wss://self-signed.badssl.com/");
	
	websocket.onopen = function (event) {
        
    };
    websocket.onclose = function (event) {
        var reason;
        alert(event.code);
        
    };
    websocket.onmessage = function (event) {
        
    };
    websocket.onerror = function (event) {
        
    };
	}
	catch(err){
	document.getElementById("demo").innerHTML = err.message;
	}
</script>
<p id="demo"></p>