js如何实现动态校验开始结束时间

<input type="date" placeholder="请输入(From)..." id="txtStartDate" value="${startDate }" onblur="onblurStartDate();" />
<input type="date" placeholder="请输入(To)..." id="txtEndDate" value="${endDate }" onblur="onblurEndDate();" />

<script type="text/javascript">
/**
 * 动态校验开始时间
 * @returns
 */
function onblurStartDate() {
	var startDateStr = $("#txtStartDate").val();
	var nowDate = new Date().toISOString().substring(0, 10); //当前时间截取操作
	var endDateStr = addDate(startDateStr, 29);
 
	if(startDateStr >= nowDate) {
		alert("开始时间不能大于等于今天！");
		var endDate = addDate(nowDate, -29);
		$("#txtStartDate").val(endDate);
		return;
	}
	if(endDateStr >= nowDate) {
		$("#txtEndDate").val(nowDate);
		return false;
	}
	$("#txtEndDate").val(endDateStr);
}
 
/**
 * 动态校验结束时间
 * @returns
 */
function onblurEndDate() {
	var endDateStr = $("#txtEndDate").val();
	var nowDate = new Date().toISOString().substring(0, 10); //当前时间截取操作
 
	if(endDateStr > nowDate) {
		alert("结束时间不能大于今天！");
		$("#txtEndDate").val(nowDate);
		var startDate = addDate(nowDate, -29);
		$("#txtStartDate").val(startDate);
		return false;
	}
	var startDateStr = addDate(endDateStr, -29);
	$("#txtStartDate").val(startDateStr);
}
 
/**
 * 日期加减法 格式:addDate('2017-01-11',20)
 * @param date计算开始的日期
 * @param days需要加的天数 （正数加，负数减）
 * @returns 计算后的时间
 */
function addDate(date, days) {
	var d = new Date(date);
	d.setDate(d.getDate() + parseInt(days));
	var m = d.getMonth() + 1;
	m = parseInt(m) < 10 &#63; ('0' + m) : m;
	var day = parseInt(d.getDate()) < 10 &#63; ('0' + d.getDate()) : d.getDate();
	return d.getFullYear() + '-' + m + '-' + day;
}
</script>

/**
 * 	页面初始化+指定时间
 * @param request
 * @param response
 * @return
 */
@RequestMapping(value = { "/pageInit.do" })
protected String pageInit(final HttpServletRequest request, final HttpServletResponse response) {
	SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
	request.setAttribute("startDate", sdf.format(TimeUtils.addDate(new Date(), -29)));
	request.setAttribute("endDate", sdf.format(new Date()));
	return "taskManage/taskindex";
}