Javascript validation and getting value of it

[eluser]gmahesha[/eluser]
Hi.. i have problem in validation of a check boxes using javascript in CI.
After submitting the form, in the validation function if i write this statement alert(document.form_name.checkbox_name.length); it will show undefined.

I think it works in without CI. but here, in CI i am getting problem.. So, anyone know how to validate the check boxes using javascript( not PHP) in CI.... plz help me

Thanks in advance.