Right now we use codemirror's JavaScript mode on the website but there's a JSX mode now so we should start using that instead.

if (!cm.state.focused) return;
    var display = cm.display;
    clearInterval(display.blinker);
    var on = true;
    display.cursor.style.visibility = display.otherCursor.style.visibility = "";
    if (cm.options.cursorBlinkRate > 0)
      display.blinker = setInterval(function() {
        display.cursor.style.visibility = display.otherCursor.style.visibility = (on = !on) ? "" : "hidden";
      }, cm.options.cursorBlinkRate);
  }
  
  function startWorker(cm, time) {