custom action after commit in form action button

hi friends

 onclick="javascript: {ddwrt:GenFireServerEvent('__commit;')}; AfterSave();" 

am using above form action button to save and popup item field

i am getting all other filed values except ID below javascript code am using to get title and id.

"var x=document.getElementById("ID");"

var x=document.getElementById("Title");

am able to get title but am not getting ID. is there any error in my code.