<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <meta charset="utf-8">
  <title></title>
  <script>
    function dateToDate(date) {
      var sDate = new Date();
      if (typeof date == 'object'
        && typeof new Date().getMonth == "function"
        ) {
        sDate = date;
      }
      else if (typeof date == "string") {
        var arr = date.split('-')
        if (arr.length == 3) {
          sDate = new Date(arr[0] + '-' + arr[1] + '-' + arr[2]);
        }
      }

      return sDate;
    }


    function addMonth(date, num) {
      num = parseInt(num);
      var sDate = dateToDate(date);

      var sYear = sDate.getFullYear();
      var sMonth = sDate.getMonth() + 1;
      var sDay = sDate.getDate();

      var eYear = sYear;
      var eMonth = sMonth + num;
      var eDay = sDay;
      while (eMonth > 12) {
        eYear++;
        eMonth -= 12;
      }

      var eDate = new Date(eYear, eMonth - 1, eDay);

      while (eDate.getMonth() != eMonth - 1) {
        eDay--;
        eDate = new Date(eYear, eMonth - 1, eDay);
      }

      return eDate;
    }

    function calcDate() {
      var d = document.getElementById('date').value;
      var n = document.getElementById('num').value;
      var eDate = addMonth(d, n);
      document.getElementById('result').innerHTML = eDate.getFullYear() + '-' + (eDate.getMonth() + 1) + '-' + eDate.getDate();
    }
  </script>
</head>
<body>
  <input type="date" id="date" />
  <input type="number" id="num" value="1" />
  <input type="button" value="計算" onclick="calcDate()" />
  <div id="result"></div>
</body>
</html>

方法二：

<script language="javascript">
Date.prototype.Format = function(fmt) 
{
//代碼作者: meizz 
var o =
{ 
"M+" : this.getMonth() + 1, //月份 
"d+" : this.getDate(), //日 
"h+" : this.getHours(), //小時 
"m+" : this.getMinutes(), //分 
"s+" : this.getSeconds(), //秒 
"q+" : Math.floor((this.getMonth() + 3) / 3), //季度 
"S" : this.getMilliseconds() //毫秒 
}; 
if (/(y+)/.test(fmt)) 
fmt = fmt.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length)); 
for (var k in o) 
if (new RegExp("(" + k + ")").test(fmt)) 
fmt = fmt.replace(RegExp.$1, (RegExp.$1.length == 1) ? (o[k]) : (("00" + o[k]).substr(("" + o[k]).length))); 
return fmt; 
}
Date.prototype.addDays = function(d)
{
this.setDate(this.getDate() + d);
};
Date.prototype.addWeeks = function(w)
{
this.addDays(w * 7);
};
Date.prototype.addMonths= function(m)
{
var d = this.getDate();
this.setMonth(this.getMonth() + m);
if (this.getDate() < d)
this.setDate(0);
};
Date.prototype.addYears = function(y)
{
var m = this.getMonth();
this.setFullYear(this.getFullYear() + y);
if (m < this.getMonth()) 
{
this.setDate(0);
}
};
</script>

方法三：

<script> 
function  DateAdd(interval,number,date) 
{ 
/* 
 *---------------  DateAdd(interval,number,date)  ----------------- 
 *  DateAdd(interval,number,date)  
 *  功能:實現(xiàn)VBScript的DateAdd功能. 
 *  參數(shù):interval,字符串表達(dá)式，表示要添加的時間間隔. 
 *  參數(shù):number,數(shù)值表達(dá)式，表示要添加的時間間隔的個數(shù). 
 *  參數(shù):date,時間對象. 
 *  返回:新的時間對象. 
 *  var  now  =  new  Date(); 
 *  var  newDate  =  DateAdd( "d ",5,now); 
 *  author:wanghr100(灰豆寶寶.net) 
 *  update:2004-5-28  11:46 
 *---------------  DateAdd(interval,number,date)  ----------------- 
 */ 
    switch(interval) 
    { 
        case  "y "  :  { 
            date.setFullYear(date.getFullYear()+number); 
            return  date; 
            break; 
        } 
        case  "q "  :  { 
            date.setMonth(date.getMonth()+number*3); 
            return  date; 
            break; 
        } 
        case  "m "  :  { 
            date.setMonth(date.getMonth()+number);
            return  date; 
            break; 
        } 
        case  "w "  :  { 
            date.setDate(date.getDate()+number*7);
            return  date; 
            break; 
        } 
        case  "d "  :  { 
            date.setDate(date.getDate()+number); 
            return  date; 
            break; 
        } 
        case  "h "  :  { 
            date.setHours(date.getHours()+number);
            return  date; 
            break; 
        } 
        case  "m "  :  { 
            date.setMinutes(date.getMinutes()+number); 
            return  date; 
            break; 
        } 
        case  "s "  :  { 
            date.setSeconds(date.getSeconds()+number); 
            return  date; 
            break; 
        } 
        default  :  { 
            date.setDate(d.getDate()+number); 
            return  date; 
            break; 
        } 
    } 
}
var  now  =  new  Date(); 
//加五天. 
var  newDate  =  DateAdd( "d ",5,now); 
alert(newDate.toLocaleDateString()) 
//加兩個月. 
newDate  =  DateAdd( "m ",2,now); 
alert(newDate.toLocaleDateString()) 
//加一年 
newDate  =  DateAdd( "y ",1,now); 
alert(newDate.toLocaleDateString()) 
</script>

以上所述就是本文的全部內(nèi)容了，希望大家能夠喜歡。

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