How to set item focus from javascript

Question

Hi all,
i need to validate a form item with javascript to check required fields.
The function is :
function isRequired(field) {
if ($v_IsEmpty(field)) {
alert('The field is required!');
html_GetElement(field).focus();
return false;
return true;
Also in the form item attribute i added :
onChange="isRequired(this);"
If the filed is null, i see the alert but the focus is on the next item! How can i set the focus on the null item?
Thanks,
Sergio

Answer 1

Denes, thanks for your answer.
I tried
html_GetElement($x(field).id).focus();
but doesn't work.
Also, if in the form item attribute i add
onBlur="isRequired(this);"
instead of
onChange="isRequired(this);"
the javascript works with both solution (html_GetElement(field).focus(); or html_GetElement($x(field).id).focus();) with IE7 but doens.t work with Firefox 3.0.1.
Please help me, please
Sergio