It is this bit of code. I condensed it a bit for readability and added my own comments.

function checkElements( e ) {
	// reset validation var and send data
	send.validationError = false;
	send.datastring = 'ajax=true';
	//	Get in js added element (e.g. from reCAPTCHA)
	send.formElements = form.find('textarea, select, input[type=text], input[type=checkbox], input[type=hidden], input[type=email]');
	
	send.formElements.each(function(i) {
		var currentElement = $(this),
		surroundingElement = currentElement.parent(),
		value = currentElement.val(),
		name = currentElement.attr('name'),
	 	classes = currentElement.attr('class'),
	 	nomatch = true;
	 	if(currentElement.is(':checkbox'))
		 	{ if(currentElement.is(':checked')) { value = true; } else { value = ''; } }
			send.dataObj[name] = encodeURIComponent(value);
		 	// P: The following is a repeated pattern of testing a condition, setting a class on the surrounding element, either 'error' or 'valid'
		 	// P: Condition: "has a value" / "not empty"
		 	if(classes && classes.match(/is_empty/)) {
				if(value == '' || value == null) {
					surroundingElement.removeClass("valid error ajax_alert").addClass("error");
					send.validationError = true;
				} else {
					surroundingElement.removeClass("valid error ajax_alert").addClass("valid");
				}
				nomatch = false;
			}
			// P: Condition: type is e-mail
			if(classes && classes.match(/is_email/)) {
				if( ! value.match(/^[\w|\.|\-]+@\w[\w|\.|\-]*\.[a-zA-Z]{2,20}$/)) {
					surroundingElement.removeClass("valid error ajax_alert").addClass("error");
					send.validationError = true;
				} else {
					surroundingElement.removeClass("valid error ajax_alert").addClass("valid");
				}
				nomatch = false;
			}
			// P: Condition: e-mail with bells and whistles
			if(classes && classes.match(/is_ext_email/)) {
				//  also allowed would be: ! # $ % & ' * + - / = ? ^ _ 
 { | } ~
				if( ! value.match( /^[\w|\.|\-|ÄÖÜäöü]+@\w[\w|\.|\-|ÄÖÜäöü]*\.[a-zA-Z]{2,20}$/ ) ) {
					surroundingElement.removeClass("valid error ajax_alert").addClass("error");
					send.validationError = true;
				} else {
					surroundingElement.removeClass("valid error ajax_alert").addClass("valid");
				}
				nomatch = false;
			}
			// P: Condition: phone number
			if(classes && classes.match(/is_phone/)) {
				if( ! value.match(/^(\d|\s|\-|\/|\(|\)|\[|\]|e|x|t|ension|\.|\+|\_|\,|\:|\;){3,}$/)) {
					surroundingElement.removeClass("valid error ajax_alert").addClass("error");
					send.validationError = true;
				} else {
					surroundingElement.removeClass("valid error ajax_alert").addClass("valid");
				}
				nomatch = false;
			}
			// P: Condition: just numbers
			if(classes && classes.match(/is_number/)) {
				if( ! value.match( /^-?\s*(0|[1-9]\d*)([\.,]\d+)?$/ ) ) {
					surroundingElement.removeClass("valid error ajax_alert").addClass("error");
					send.validationError = true;
				} else {
					surroundingElement.removeClass("valid error ajax_alert").addClass("valid");
				}
				nomatch = false;
			}
			// P: Condition: positive number
			if(classes && classes.match(/is_positiv_number/)) {
				if(!($.isNumeric(value)) || value == "" || value < 0 ) {
					surroundingElement.removeClass("valid error ajax_alert").addClass("error");
					send.validationError = true;
				} else {
					surroundingElement.removeClass("valid error ajax_alert").addClass("valid");
				}
				nomatch = false;
			}
			// P: Handle the captcha
			if(classes && classes.match(/captcha/) && ! classes.match(/recaptcha/) ) {
				var verifier 	= form.find("#" + name + "_verifier").val(),
					lastVer		= verifier.charAt(verifier.length-1),
					finalVer	= verifier.charAt(lastVer);
				if(value != finalVer) {
					surroundingElement.removeClass("valid error ajax_alert").addClass("error");
					send.validationError = true;
				} else {
					surroundingElement.removeClass("valid error ajax_alert").addClass("valid");
				}
				nomatch = false;
			}
			// P: And HERE is my problem: if a form field has any value and it has no specific validation set, 'nomatch' will be true and this condition will hit. The return value will be "valid". However, if a form field has nothing filled in and is has no specific validation set, there is no remaining way for it to validate and hence that situation gets stuck without a 'valid' class.
			if(nomatch && value != '')
						{
							surroundingElement.removeClass("valid error ajax_alert").addClass("valid");
						}
				});

I found the effects as such: the form would not work and it would invalidate (red line around it, i.e. a class that matched the CSS for that red line) on all field without validation that were empty.

I changed the line
if(nomatch && value != '')
to
if(nomatch)

and it solved my problems.

I hope this clears up the core issue. My further suggestions for splitting out validation on content (“if there is a value, does it conform to the data type set, i.e. is a number a number and is a date a date”) and validation for mandatory presence (“does there need to be a value for the form to accept processing”) you can ignore.

• This reply was modified 4 years, 6 months ago by KdvPebbels.

As an alternative, you could have an explicit “do not validate” class, rather than relying on finding nothing. Even better (because I find this a mild design flaw): separate out the options for validation of a value being a certain data type and it being a required field. It would be an additional checkbox in the admin interface and you would need to do some upgrade logic (or fall back to a sensible default) but it would follow two distinct validation paths:

1) is there a data type indicated –> (yes –> validate against regex; no –> ContenttypeValid = true)
2) should there be a value –> (yes –> good / nogood; no –> ContentPresentValid = true; don’t know –> data type set ==> assume yes –> good / nogood)

Then take ContentTypeValid && ContentPresentValid as a prerequisite for posting the form.