As i said before, the data are being added to the stockGenerators variable (it takes some times), so when the subscribe function is called, it will not send anything to Lightstreamer server (because that item is not found "yet" in stockGenerators variable), so myFeed.sendCurrentValues(itemName); will return nothing. That's why data will not be shown in the browser.
I think it will be shown only when you refresh the session (after you close the browser, and wait a while).
Is there a solution to call the subscribe function when you refresh the page ? Or is there a way when you close the browser or page, you kill the session ( so i don't have to wait some time before the session get killed) ?