How to get timesheet information in a javascript (Project Server 2013)

Question

Hi all,
In Project Server 2013, I'm trying to customize the Timesheet ribbon. This far, I've been able to add a new button and tie an event to it. All is working well. This is all done using elements.xml and a javascripts.
Now the problem is that I want to get some informations about the timesheet (the Guid for example) and, for now, I've got no success. I know that there is an object called PS.TimeSheet, but when I try to use some PS.TimeSheet's methods I get an error.
Note that i'm in the page http://servername/pwa/timesheet.aspx (there is not Guid in the address) and all the treatments should be done in the javascript (no call to another aspx page)
Thanks !

Answer 1

Finally, I've found the solution.
My goal was to add a button in the timesheet ribbon to launch a special report showing some data about the timesheet. The report has the timesheet Guid as parameter.
To customize the Sharepoint ribbon, you have to do it via an xml file and a javascript (a lot of explanation is available in the internet that explains how to do it). So I had to call a function in the javascript to launch the report (which is a SSRS report).
When you are in a javascript you have access to many global variables. When the timesheet.aspx is displayed, there is a global variable called "timesheetComponent".
Using this variable we can call the method :
timesheetComponent.m_consumedApi.get_Impl()
to get an implementation of the current timesheet. This implementation has an attibute that has a lot of nice stuff about the current user and the current time sheet. This attribute is 
_headerInfo
_headerInfo is a structure that includes tsUid which contains the timesheet Guid I was looking for.
Finally, the function attached to the button goes like this :
function _LaunchReport() {
var tsUId;
var rptPath;
var tsImpl = timesheetComponent.m_consumedApi.get_Impl();
try
if (CONST_REPORT_PATH == null || CONST_REPORT_PATH == "" ) {
alert("Constant CONST_REPORT_PATH is not defined")
else {
tsUId = tsImpl._headerInfo.tsUid;
rptPath = CONST_REPORT_PATH + 'TimesheetDetails&rs:Command=Render&rc:Parameters=false&TimesheetUID=' + tsUId;
window.open(rptPath);
catch (Err) {
alert(Err)
CONST_REPORT_PATH is the path to SSRS defined elsewhere
I hope this will help some other poeple !