Javascript 无法循环通过<；李>；Items JQUERY

我想循环查看我的li项目，找到之前列表中已经存在的类似项目，并将其替换为新项目。实际上，我正在使用SignalR制作一个聊天应用程序，我想在其中显示在线用户，一旦用户登录，就会提供并显示来自Db的完整用户列表，然后如果有任何其他用户在线，则只会在已登录用户的列表中添加他的姓名。我的代码是这样的

       chatProxy.client.onlineUser = function (type,list,user,connID,uniqueID) {

            listItems = $("#onlineuser").find("li").each(function () {
                var product = $(this).attr('class');
                alert(product);
            });

            if (type == "NewUser") {
                for (var i in list) {

                    $("#onlineuser").append(ulamker(list[i]['UserName'], list[i]['Status'], "Your Last Message"));

                }


                    function ulamker(name, status, lastmessage) {
                        if (status == "ONLINE") {
                            var finalstring = '<li class="online active" user=' + list[i]['UserName'] + ' userId=' + list[i]['Userid'] + ' connectionID=' + list[i]['ConnectionId'] + '><a class="media"><img class="media-object " src="/Content/img/avatar7.jpg" alt=""> <div class="media-body"><span class="name"><span class="message leftmenuname namehighlight">' + name + ' </span></span>  <span class="badge badge-outline status"></span> </div> </a> </li>'

                            return finalstring;
                        }
                        else if (status == "OFFLINE")
                        {
                            var finalstring = '<li class="offline" user=' + list[i]['UserName'] + ' userId=' + list[i]['Userid'] + ' connectionID=' + list[i]['ConnectionId'] + '><a class="media"><img class="media-object" src="/Content/img/avatar7.jpg" alt=""> <div class="media-body"><span class="name"><span class="message leftmenuname namehighlight">' + name + ' </span></span>  <span class="badge badge-outline status"></span> </div> </a> </li>'

                            return finalstring;
                        }
                    };
                   

                }


            else if (type == "OldUser") {


               
                $("#onlineuser").append(ulamker1(user, connID, "Online", "Your Last Message"));

                function ulamker1(name, connection, status, lastmessage) {
                    if (status == "Online") {
                        var finalstring = '<li class="online active" username=' + user + ' userId=' + uniqueID + ' connectionID=' + connID + '><a class="media"><img class="media-object " src="~/Content/img/avatar7.jpg" alt=""> <div class="media-body"><span class="name"><span class="message leftmenuname namehighlight">' + name + ' </span></span> <span class="badge badge-outline status"></span> </div> </a> </li>'

                        return finalstring;
                    }
                };
               

            }
            else
            {

            }

        };

         listItems = $("#onlineuser").find("li").each(function () {
                var product = $(this).attr('class');
                alert(product);
            });