请问这是什么意思吗

 title.onclick = function(event) {
        event = event || window.event;
        event.stopPropagation ? event.stopPropagation() : event.cancelBubble = true;
        if(box.className == "extended"){
          resetM();
        } else {
          box.className = "extended";
          menu.className = "anim_extendDown animated speed_fast";
          menu.style.display = "block";
        }
      }