Data is automatically sorted when return from Java to Javascript

I use DWR to load data into a drop-down when another drop-down is changing. This is the Javascript.

ClassX.loadData(StudentId
            function(data){
                console.log(data);
            }
        );

I pass Map from Java to above JavaScript. This Map is sorted in the server side with it's value.But when check the Map in the console above, they are sorted automatically with it's key values. Is there anyway to stop this automatically sorting and retrieve the original values sent from server?What is the reason for this?