Get the Control ID in javasscript from Usercontrol or Data grid

use the given javascript to  get the control client id in javascript from user control or data grid

function GetClientId(strid)
{
     var count=document.forms[0].length;
     var i=0;
     var eleName;
     for (i=0; i < count; i++ )
     {
       eleName=document.forms[0].elements[i].id;
       pos=eleName.indexOf(strid);
       if(pos>=0)  break;           
     }
    return eleName;
 }