jquery.validate-选与反选思路

	//code to hide topic selection, disable for demo
	var newsletter = $("#newsletter");
	// newsletter topics are optional, hide at first
	var inital = newsletter.is(":checked");
	alert(inital)
	var topics = $("#newsletter_topics")[inital ? "removeClass" : "addClass"]("gray");
	var topicInputs = topics.find("input").attr("disabled", !inital);
	// show when newsletter is checked
	newsletter.click(function() {
		alert(this.checked)
		topics[this.checked ? "removeClass" : "addClass"]("gray");
		topicInputs.attr("disabled", !this.checked);
	});