The jQuery Validation `valid()` method returns 0 when required is not true

Question

I'm using the jQuery Validation plugin and I've got a textbox with the class digits to force it to be digits only, but not required. When I call validate on the form it works fine, but if I call valid() on the textbox when it's empty, it returns 0, despite no error message showing and required not being set.

Does anyone know why it would be returning this for a seemingly valid input value?

Here is the code:

<input type="text" value="" name="kiloMetresTravelled" id="kiloMetresTravelled" class="digits"/>

and the script

<script type="text/javascript'>
 var isvalid = jQuery('#kiloMetresTravelled').valid(); 
 //isvalid == 0 when kiloMetresTravelled is blank
</script>

Solution

Check this, from the documentation:

Makes "field" required and digits only.

You could do something like this:

var isValid = jQuery('#kiloMetresTravelled').valid() || jQuery('#kiloMetresTravelled').val() == "";

Comments

[Glenn Slaven]

Doesn't it only say 'makes the element require digits only'. They added a 'required' rule as well

[JT.]

The example adds the required rule into the mix: this answer is misleading. What actually happens is that since there is no required rule on the field, the internal 'check' method returns undefined for the field in question. Why this is so is a mystery to me. Note that the code above works but (a) the reason is wrong, and (b) it will only work for a single element under test.