How to check if javascript has run in codebehind ( c# )?

[Visslan]

codeInfront:

<input type="button" onclick="JavaScript:clearSelections();" name="clear" value="Delete"/>

codeBehind:

public void Page_Init( object sende, System.EventArgs e )
{
   if( ?input button has been klicked? )
   {
       .....
   }
}

In my code behind I want to reset an object when the button has been klicked. But how can I see if that has happened?