js判断当前时间前几天和格式校验

function time(addday)

{

	var now= new Date();

	nowdate=now.getDate();

	//alert(nowdate);

	now.setDate(nowdate+addday);//获取addday天后的日期

	year=now.getFullYear();

	month=now.getMonth();

	date=now.getDate();

	return now;

}

<script>

	function getBeforeDate(n){

		var n = n;

		var d = new Date();

		var year = d.getFullYear();

		var mon=d.getMonth()+1;

		var day=d.getDate();

		if(day <= n){

			if(mon>1) {

			        mon=mon-1;

			 }

			else {

			     year = year-1;

			     mon = 12;

			  }

		}

		d.setDate(d.getDate()-n);

		 year = d.getFullYear();

		mon=d.getMonth()+1;

		day=d.getDate();

		s = year+"-"+(mon<10?('0'+mon):mon)+"-"+(day<10?('0'+day):day);

		return s;

	}

</script>

$("#go").click(function(){

	//alert(getBeforeDate(341));

	var projectname="<%=session.getAttribute("projectname_session")%>";

	var modelname= document.getElementById("codeid").value;

	var d=document.getElementById("enddate").value;

	var year= d.substring(0,4);

	var mon=d.substring(5,d.lastIndexOf("-"));

	var day=d.substring(d.lastIndexOf("-")+1,d.length);

	var selectDate = year+"-"+((mon.length==1)?('0'+mon):mon)+"-"+(day.length==1?('0'+day):day);

	 alert(selectDate);

	//alert(selectDate);

	if(selectDate<=getBeforeDate(341)||(selectDate>=getBeforeDate(-1))){

		var info="No Data!\r\nPlease Select a Valid Date: \""+getBeforeDate(341)+" ~ "+getBeforeDate(0)+"\"";

		alert(info);

	}

	else{

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