js 根据天数算日期

浏览数：59 / 时间：2015年06月09日

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=windows-1250">
<meta name="generator" content="PSPad editor, www.pspad.com">
<title></title>
</head>
<body>

<script type="text/javascript">

alert(showDate(20));

function showDate(calValue) {

     var dateObj = new Date();
     var curYear = dateObj.getFullYear();
     var curMonth = dateObj.getMonth() + 1;
     var curDate = dateObj.getDate();

  curMonth = curMonth > 9 ? curMonth : "0" + curMonth;
  curDate = curDate > 9 ? curDate : "0" + curDate;
  var dateParameter = curYear + "/" + curMonth + "/" + curDate;
     var returnDate = "";
     returnDate = calculateDate(dateParameter, calValue);

     return returnDate;
}

function calculateDate(dateParameter, calValue) {
    var calValue = Number(calValue);
    var newDate = new Date(dateParameter);
    //返回日期的毫秒值
    newDate = newDate.valueOf();
    //加/减天数后的毫秒值
    newDate = newDate + calValue * 24 * 60 * 60 * 1000;
    newDate = new Date(newDate);

    //如果月份长度少于2，则前加 0 补位
    var month = newDate.getMonth()+1;
    var month = month > 9 ? month : "0" + month;

    //如果天数长度少于2，则前加 0 补位
    var date = newDate.getDate();
    var date = date > 9 ? date : "0" + date;

    var returnDate = newDate.getFullYear() + "-" + month + "-" + date;
    return returnDate;
   }

</script>
</body>
</html>