Jak nastavit focus pro prvek u manualne vytvareneho formulare

Mam jednoduchou sablonu:

{control loginForm begin}

{foreach $flashes as $flash}
 <p class="flash-message">{$flash->message}</p>
{/foreach}

{assign errors => $control['loginForm']->errors}
 <p class="error" n:if="$errors" n:foreach="$errors as $error">{$error}</p>

 <table>
   <tr>
     <td class="upper" colspan="2">
       <b><font size='1px'>::: LOGIN :::</font></b>
     </td>
   </tr>
   <tr>
     <td colspan="2" height="5"></td>
   </tr>
   <tr>
     <td class="labels">
       {$control['loginForm']['username']->label}
     </td>
     <td>
       {$control['loginForm']['username']->control}
     </td>
   </tr>
   <tr>
     <td class="labels">
       {$control['loginForm']['password']->label}
     </td>
     <td>
       {$control['loginForm']['password']->control}
     </td>
   </tr>
   <tr>
     <td colspan="2" height="5"></td>
   </tr>
   <tr>
     <td class="lower" colspan="2">
       <input type="submit" style="margin-left:230px;" value="Submit">
     </td>
   </tr>
 </table>
 {control loginForm end}

username, kteremu bych chtel nastavit focus se prevede na toto HTML:

<input type="text" class="text" name="username" id="frmloginForm-username" value="" />

Rad bych nastavil focus jednoduse takto: document.getElementById(„<id>“) .. nicmene nevim, jakym zpusobem zjistit soucasne ID (tj. frmloginForm-username – natvrdo to davat do JS nechci), pripadne jak ho zmenit.

Predem diky za odpoved!