HTML Form Validation - Conditional based on radio button selection [duplicate]

Answer 1

From: https://stackoverflow.com/a/19546185/1477051

jQuery Validate actually directly supports this, using dependency expressions.

All you need to do is change your validate options like this:

$('#myform').validate({
    rules: {
        fieldA: {
           required:'#checkA:checked'
        }
    }
});

That's it!

I've used it on your code here: http://jsfiddle.net/xJBX9/1/