How to get id of the control causes postback in javascript

[Whaweretheythinkin]

How can I get the id of the control which causes \[code\]PostBack\[/code\] in asp.net. I uses \[code\]document.getElementById("__EVENTTARGET")\[/code\]But it is giving only \[code\]objectHtmlInputElement\[/code\] Not a complete ID. How Can I get this in javascript only and not in code behind. I want this for focusing on that element after postback. Please help..