jQuery event for better testing, whether value has changed

jQuery.valueChange.js

$.fn.valueChange = function (onChange) {
	var form = $(this);

	var valueChange = {
		trigger : function (event) {
			$(event.target).trigger('valueChange');
		},

		store : function (event) {
			// saves the actual value to data attribute
			var et = $(event.target);

			// actual value
			et.data('vch-val', et.val()).data('vch-children', et.children().length);
		},

		testAndTrigger : function (event) {
			// compares the saved value and actual value, to decide, whether trigger event or not
			var et = $(event.target);
			if (et.data('vch-children') != et.children().length) {
				et.data('vch-val', et.val()).data('vch-children', et.children().length);
				return ;
			}

			if (et.data('vch-val') != et.val()) {
				et.data('vch-val', null).trigger('valueChange');
			}
		},

		setupDatepicker : function () {
			form.find('.hasDatepicker').change(valueChange.trigger);
		}
	};

	if (form.length > 1 || form[0].nodeName.toLowerCase() != 'form') {
		form.each(function () {
			var el = $(this);

			if (el.hasClass('vch-notstart')) {
				return ;
			}

			el.bind('valueChange', onChange);
			if (el[0].nodeName.toLowerCase() == 'select') {
				el.focus(valueChange.store).change(valueChange.testAndTrigger);

			} else {
				if (el.attr('type').toLowerCase() == 'text' || el[0].nodeName.toLowerCase() == 'textarea') {
					el.bind('focus click', valueChange.store).blur(valueChange.testAndTrigger);

				} else if (el.attr('type').toLowerCase() == 'checkbox' || el.attr('type').toLowerCase() == 'radio') {
					el.change(valueChange.trigger);

				} else if (el.attr('type').toLowerCase() == 'submit' || el[0].nodeName.toLowerCase() == 'button') {
					el.click(valueChange.trigger);
				}
			}
		});

	} else {
		form.find(':input:not(.vch-notstart)')
			.bind('valueChange', onChange);

		form.find(':text:not(.vch-notstart), textarea:not(.vch-notstart)')
			.bind('focus click', valueChange.store).blur(valueChange.testAndTrigger);

		form.find(':checkbox:not(.vch-notstart), :radio:not(.vch-notstart)')
			.change(valueChange.trigger);

		form.find('select:not(.vch-notstart)')
			.focus(valueChange.store).change(valueChange.testAndTrigger);
	}

	$(document).ajaxComplete(valueChange.setupDatepicker);
};

$('form#target').valueChange(function (e) { alert('value of ' + e.target.id + ' has changed!'); });