SF Odata to retrieve current logged in user in browser

Dear Experts,

We are trying to retrieve current logged in user in Successfactors instance from Odata call.

We are able to get the user details by odata call and  passing the username ( admin)  as below -

var service_url= "https://<datacenter>.successfactors.com/odata/v2/User(%27admin%27)/?$format=json";

oModel.loadData(service_url,null,false, "GET", false, false, null);

var username = oModel.getData().d.username;

But we would like to read the logged in user and use in the code above . So that we can get user details for every logged in user and not a particular user ex - admin.

Any inputs are greatly appreciated .

Thanks,
Sahiba Gandhi