Function eventSupported

Picviewer CE+/dist.user.js:13654–13671

( eventName,elem )

        //事件支持检测.
        function eventSupported( eventName,elem ){
            elem = elem || document.createElement("div");
            eventName = "on" + eventName;
            var isSupported = (eventName in elem);
            if (!isSupported){
                if(!elem.setAttribute){//setAttribute是元素节点的方法
                    elem=document.createElement("div");
                };
                var setAttr;
                if(!elem.hasAttribute(eventName)){
                    setAttr=true;
                    elem.setAttribute(eventName, "return;");
                };
                isSupported = typeof elem[eventName] == "function";
                if(setAttr)elem.removeAttribute(eventName);
            }
            return isSupported;
        }


        //检测属性支持.dom属性