JQuery $(":checkbox").attr("checked", "") でチェックをはずす

ブランク、null、未定義値の場合 removeに流す

$(document).ready(function(){
/*
	$.fn.origAttr = $.fn.attr;
	$.fn.attr = function(key,value) {
		if (value == "" || value == null || value == undefined) {
			this.removeAttr(key);
		} else {
			this.origAttr(key, value);
		}
		return $(this);
	}
*/
	$.fn.origAttr = $.fn.attr;
	$.fn.attr = function(key, value) {
		var keys = [ 
			"checked", "selected", "requred", "multiple", "readonly", 
			"disabled", "standby", "compact", "declare", "defer", "ismap", 
			"nohref", "noresize", "noshade", "nowrap" 
		];
		var regexpKeys = "/(" + keys.join("|") + ")/ig";
		if (typeof key == "string") {
			if (key.match(regexpKeys) == null) {
				$(this).origAttr(key, value);
			} else if (value == 0 || !!value){
				$(this).origAttr(key, value);
			} else {
				$(this).removeAttr(key);
			}
		} else {
			$(this).origAttr(key, value);
		}
		return $(this);
	};
});