thanks Harish/Dustin,
We can be able to auto populate Approver value. But i want to get Cost centre value as well .the below script used to get the approver value.
Client Script:
c.deliverTo = c.data.location;
$scope.$on("field.change", function(evt, parms) {
  if (parms.field.name == 'requested_for') { //detects that requestor name has changed
   c.deliverTo = '';
c.data.u_approver ='';
   c.server.get({ //send the server the new user ID & action is to update the location
    userID: parms.newValue,
    action: "get_user_location"
   }).then(function(response) {
alert(response.data.location);
    c.data.u_approver = {
displayValue: response.data.location,
value: response.data.location,
name: response.data.location
};
   });
   }
});
~~~~~~~~~~~~~~~~~~~~
Server Script:
if (input && input.action === "get_user_location") {
  userID = input.userID;
}
data.location = getUserLocation(userID);
function getUserLocation(userSysID) {
var sysUserGR = new GlideRecord("sys_user");
  sysUserGR.get(userSysID);
  var newLocation = sysUserGR.getElement("manager");
  return newLocation.getDisplayValue();
}
where i need to add to get cost centre value
