add ping interval from datalad page

Author: katjaq

ohbm2020/room.html

@@ -74,13 +74,16 @@
         let wss = new ReconnectingWebSocket("wss://dev1.soichi.us/ohbm2020/");
         // let wss = new WebSocket("wss://dev1.soichi.us/ohbm2020/");
         wss.onopen = () => {
+          wss.send(JSON.stringify({action: "jit", id, cid}));
+          setInterval(()=>{
             wss.send(JSON.stringify({action: "jit", id, cid}));
-        }
+          }, 1000*30);
+        };
+
         window.addEventListener("beforeunload", function(evt) {
             wss.send(JSON.stringify({action: "jitclose", id, cid}));
         });
 
-
         function feedbackAnimationStep(timer, elem) {
           const dx = 500 * Math.random() - 250;
           const x = parseInt("0" + elem.style.left);