array of checkboxes

[Anon]

I'm sorry if this is a little off topic. I have a form that has several checkboxes that pass an array to a PHP form handeler.

<input type="checkbox" name="books_ordered[]" value="book1">
<input type="checkbox" name="books_ordered[]" value="book2">
<input type="checkbox" name="books_ordered[]" value="book3">

This will send an array ($books_ordered) containing all of the books ordered, simple enough. I have some server-side form validation by running count() on the array (to make sure at least one book is checked). How would I do the same form validation in javascript (check the number in indexes in $books_ordered to make sure at least one book is selected)?

thanks

[Anon]

I have shown you below that atleast first checkbox should be selected.. you can make it for all the checkboxes like
...

document.form1[0].checked == false or document.form1[1].checked == false

and so on..

<script language="javascript">
function check()
{

if (document.form[0].checked == false)
{
alert("Please Select first checkbox To Proceed!!");
return false;
}
return true;
}
</script>

[Anon]

I understand you can check the true/false of each checkbox. My question was really about how to check the count of the whole array (which would acheive the same result with less code).