recjectConnectionn not rejecting .

The following is a code snippet that i'm trying to use to expell a banned user from my chat....everything works great except the rejectConnection part for some reason no matter how i set it will not reject the connection can you spot the trouble?

application.onConnect = function(client,userName,userType) {

var a = application.banned_so.getProperty("banned_so");
        for(i=0;i<a.length;i++){
         if (a==userName) {
             var errorObj = new Object();
             errorObj.msg = "You are banned";
             application.rejectConnection(client, errorObj);
             break;
            
         };
     };