jQuery Validate: Required If Visible

I needed a generic "required if visible" rule for use with the jQuery Validation plugin. This is the result:

// jQuery.validate.requiredIfVisible.js
// Copyright (c) 2010 Ori Peleg, http://orip.org, distributed under the MIT license
(function($) {
$.validator.addMethod(
"requiredIfVisible",
function(value, element, params) {
function isVisible(e) {
// the element and all of its parents must be :visible
// inspiration: http://remysharp.com/2008/10/17/jquery-really-visible/
return e.is(":visible") && e.parents(":not(:visible)").length == 0;
}

if (isVisible($(element))) {
// call the "required" method
return $.validator.methods.required.call(this, $.trim(element.value), element);
}

return true;
},
$.validator.messages.required
);
})(jQuery);

Notes:

• Using required:"#myinput:visible" could have worked, but ":visible" doesn't check for hidden parents, and I didn't want to repeat the element selector.
• ":hidden" is false for elements with the "visibility:hidden" CSS rule, so I couldn't use ":not(:hidden)" either.
• Technique for checking element visibility from Remy Sharp's blog.