<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function () {
var userid = _spPageContextInfo.userId;
function GetCurrentUser() {
var requestUri = _spPageContextInfo.webAbsoluteUrl + "/_api/web/getuserbyid(" + userid + ")";
var requestHeaders = { "accept" : "application/json;odata=verbose" };
$.ajax({
  url : requestUri,
  contentType : "application/json;odata=verbose",
  headers : requestHeaders,
  success : onSuccess,
  error : onError
});
}
function onSuccess(data, request){
 var loginName = data.d.Title;
 SetUserFieldValue("people",loginName);
}
function onError(error) {
  //alert(error);
}
function SetUserFieldValue(fieldName, userName) {
	var _PeoplePicker = $("div[title='" + fieldName + "']");
	var _PeoplePickerTopId = _PeoplePicker.attr('id');
	var _PeoplePickerEditor = $("input[title='" + fieldName + "']");
	_PeoplePickerEditer.val(userName);
	var _PeoplePickerObject = SPClientPeoplePicker.SPClientPeoplePickerDict[_PeoplePickerTopId];
	_PeoplePickerObject.AddUnresolvedUserFromEditor(true);
}
GetCurrentUser();
});
</script>