How to verify if current user is a SCA (Site Collection Administrator)?

I have a NavBar at my master page that will only be displayed to the SCA (Site Collection Administrators). I'm using jquery SPServices to do that validation, but the only examples that i found suggest to do this by validating the users group. And with some more research, I also discovered that the SCA aren't a group.

   $(document).ready( function ()
            {
                var isUserOnly = false; //User group member only
              var isAdmin=false;
        var ADMINGROUP = "Administradores de conjunto de sites";  // SPGroup named “Admin”

                $().SPServices
                ({
                  operation: "GetGroupCollectionFromUser", //Calling GetGroupCollectionFromUser.asmx web service
                  userLoginName: $().SPServices.SPGetCurrentUser(), //Calling Current User
                  async: false,
                  completefunc: function(xData, Status)
                  {                           $(xData.responseXML).find("Groups").each(function() //Retrieving the values from Group method of Web Service
                                    {
                                         $(this).find("Group").each(function()  //Parsing through all the groups the current user belongs to
                                         {
                    //Checking whether Current User belongs to Admin Group
                                              if(($(this).attr("Name").toLowerCase() === ADMINGROUP.toLowerCase()))
                                                isAdmin = true;

                    //If Current User does not belong to Admin, then definitely a normal user
                      else
                        isUserOnly=true;
                                         });
                                    });
                     }
               }); // Closing SPServices Method
    if(!isAdmin){document.getElementById('sideNavBox').style.visibility = 'hidden';}
    });`

---

I Also found this one, but i'm not quite sure how to use it (i tried):

    function isCurrentUserSiteAdmin(OnSuccess,OnError)
    {
    var context = SP.ClientContext.get_current();
    var user = context.get_web().get_currentUser();
        context.load(user);

        context.executeQueryAsync(
            function() {
              var isSiteAdmin = user.get_isSiteAdmin();  
              OnSuccess(isSiteAdmin);
            },
            OnError
        );
    }

    //Usage
    isCurrentUserSiteAdmin(function(isAdmin){
            console.log(isAdmin);
        },function(sender,args){
            console.log('An error occured: ' + args.get_message());
        }
    );

Any help is welcome! Thanks in advance.

P.S: if you know another way, let me know too!