jQuery checkbox 保存选中项时除去已经选中项

function addCommunity() {
   $(".communityClass:checked").each(function(index) {
	var communityId = $(this).val();
	if (isCommunityIdExists(communityId)) {
		var communityName = $(this).attr("communityName");
		var cityName=$(this).attr("cityName");
		var trStr = '<tr>'
		        + '<input type="hidden" name="communityIds"  value="'
			    + communityId
				+ '" /><td style="text-align:center">'
				+ cityName
				+ '</td><td style="text-align:center">'
				+ communityName
				+ '</td><td style="text-align:center"><a href="javascript:void(0)" class="pn-opt" onclick="$(this).parents(\'tr:first\').remove();">刪除</a></td></tr>';
		
		$("#commtbody").append(trStr);
	}
  });
	closeDialog('communityDiv');
}

function isCommunityIdExists(communityId) {
	if ($("input[name=communityIds][value=" + communityId + "]").length == 0) {
		return true;
	}
	return false;
}