有三个下拉列表框:年,月,日,我选了年和月之后日的列表框能否自动识别当前月份有多少天??

取出来就是31天，但实际上不用这么复杂。
你可以在年月日取完之后判断日期是否正确。
tmpstr=year.value+"-"+month.value+"-"+day.value
if not isdate(tmpstr) then
   不是正确的日期，比如2001-2-30
end if
源代码：要完成此效果需要两个步骤第一步：把如下代码加入到<head>区域中<SCRIPT language=JavaScript1.2>
isIE = (document.all ? true : false);function getIEPosX(elt) { return getIEPos(elt,"Left"); }
function getIEPosY(elt) { return getIEPos(elt,"Top"); }
function getIEPos(elt,which) {
iPos = 0
while (elt!=null) {
  iPos += elt["offset" + which]
  elt = elt.offsetParent
}
return iPos
}function getXBrowserRef(eltname) {
return (isIE ? document.all[eltname].style : document.layers[eltname]);
}function hideElement(eltname) { getXBrowserRef(eltname).visibility = 'hidden'; }// 按不同的浏览器进行处理元件的位置
function moveBy(elt,deltaX,deltaY) {
if (isIE) {
  elt.left = elt.pixelLeft + deltaX;
  elt.top = elt.pixelTop + deltaY;
} else {
  elt.left += deltaX;
  elt.top += deltaY;
}
}function toggleVisible(eltname) {
elt = getXBrowserRef(eltname);
if (elt.visibility == 'visible' || elt.visibility == 'show') {
   elt.visibility = 'hidden';
} else {
   fixPosition(eltname);
   elt.visibility = 'visible';
}
}function setPosition(elt,positionername,isPlacedUnder) {
positioner = null;
if (isIE) {
  positioner = document.all[positionername];
  elt.left = getIEPosX(positioner);
  elt.top = getIEPosY(positioner);
} else {
  positioner = document.images[positionername];
  elt.left = positioner.x;
  elt.top = positioner.y;
}
if (isPlacedUnder) { moveBy(elt,0,positioner.height); }
}//——————————————————————————————————————         // 判断浏览器
         isIE = (document.all ? true : false);         // 初始月份及各月份天数数组
         var months = new Array("一　月", "二　月", "三　月", "四　月", "五　月", "六　月", "七　月",
"八　月", "九　月", "十　月", "十一月", "十二月");
         var daysInMonth = new Array(31, 28, 31, 30, 31, 30, 31, 31,
            30, 31, 30, 31);
var displayMonth = new Date().getMonth();
var displayYear = new Date().getFullYear();
var displayDivName;
var displayElement;         function getDays(month, year) {
            //测试选择的年份是否是润年？
            if (1 == month)
               return ((0 == year % 4) && (0 != (year % 100))) ||
                  (0 == year % 400) ? 29 : 28;
            else
               return daysInMonth[month];
         }         function getToday() {
            // 得到今天的日期
            this.now = new Date();
            this.year = this.now.getFullYear();
            this.month = this.now.getMonth();
            this.day = this.now.getDate();
         }         // 并显示今天这个月份的日历
         today = new getToday();         function newCalendar(eltName,attachedElement) {
    if (attachedElement) {
       if (displayDivName && displayDivName != eltName) hideElement(displayDivName);
       displayElement = attachedElement;
    }
    displayDivName = eltName;
            today = new getToday();
            var parseYear = parseInt(displayYear + '');
            var newCal = new Date(parseYear,displayMonth,1);
            var day = -1;
            var startDayOfWeek = newCal.getDay();
            if ((today.year == newCal.getFullYear()) &&
                  (today.month == newCal.getMonth()))
    {
               day = today.day;
            }
            var intDaysInMonth =
               getDays(newCal.getMonth(), newCal.getFullYear());
            var daysGrid = makeDaysGrid(startDayOfWeek,day,intDaysInMonth,newCal,eltName)
    if (isIE) {
       var elt = document.all[eltName];
       elt.innerHTML = daysGrid;
    } else {
       var elt = document.layers[eltName].document;
       elt.open();
       elt.write(daysGrid);
       elt.close();
    }
} function incMonth(delta,eltName) {
   displayMonth += delta;
   if (displayMonth >= 12) {
     displayMonth = 0;
     incYear(1,eltName);
   } else if (displayMonth <= -1) {
     displayMonth = 11;
     incYear(-1,eltName);
   } else {
     newCalendar(eltName);
   }
} function incYear(delta,eltName) {
   displayYear = parseInt(displayYear + '') + delta;
   newCalendar(eltName);
} function makeDaysGrid(startDay,day,intDaysInMonth,newCal,eltName) {
    var daysGrid;
    var month = newCal.getMonth();
    var year = newCal.getFullYear();
    var isThisYear = (year == new Date().getFullYear());
    var isThisMonth = (day > -1)
    daysGrid = '<table border=1 cellspacing=0 cellpadding=2><tr><td bgcolor=#ffffff nowrap>';
    daysGrid += '<font face="courier new, courier" size=2>';
    daysGrid += '<a href="javascript:hideElement(\'' + eltName + '\')">x</a>';
    daysGrid += '  ';
    daysGrid += '<a href="javascript:incMonth(-1,\'' + eltName + '\')">« </a>';     daysGrid += '<b>';
    if (isThisMonth) { daysGrid += '<font color=red>' + months[month] + '</font>'; }
    else { daysGrid += months[month]; }
    daysGrid += '</b>';     daysGrid += '<a href="javascript:incMonth(1,\'' + eltName + '\')"> »</a>';
    daysGrid += '   ';
    daysGrid += '<a href="javascript:incYear(-1,\'' + eltName + '\')">« </a>';     daysGrid += '<b>';
    if (isThisYear) { daysGrid += '<font color=red>' + year + '</font>'; }
    else { daysGrid += ''+year; }
    daysGrid += '</b>';     daysGrid += '<a href="javascript:incYear(1,\'' + eltName + '\')"> »</a><br>';
    daysGrid += ' Su Mo Tu We Th Fr Sa <br> ';
    var dayOfMonthOfFirstSunday = (7 - startDay + 1);
    for (var intWeek = 0; intWeek < 6; intWeek++) {
       var dayOfMonth;
       for (var intDay = 0; intDay < 7; intDay++) {
         dayOfMonth = (intWeek * 7) + intDay + dayOfMonthOfFirstSunday - 7;
if (dayOfMonth <= 0) {
           daysGrid += "   ";
} else if (dayOfMonth <= intDaysInMonth) {
   var color = "blue";
   if (day > 0 && day == dayOfMonth) color="red";
   daysGrid += '<a href="javascript:setDay(';
   daysGrid += dayOfMonth + ',\'' + eltName + '\')" '
   daysGrid += 'style="color:' + color + '">';
   var dayString = dayOfMonth + "</a> ";
   if (dayString.length == 6) dayString = '0' + dayString;
   daysGrid += dayString;
}
       }
       if (dayOfMonth < intDaysInMonth) daysGrid += "<br> ";
    }
    return daysGrid + "</td></tr></table>";
} function setDay(day,eltName) {
   displayElement.value = (displayMonth + 1) + "/" + day + "/" + displayYear;
   hideElement(eltName);
}
//——————————————————————————————————————
// fixPosition() 这个函数和前面所讲的那个函数一样
//
function fixPosition(eltname) {
elt = getXBrowserRef(eltname);
positionerImgName = eltname + 'Pos';
// hint: try setting isPlacedUnder to false
isPlacedUnder = false;
if (isPlacedUnder) {
  setPosition(elt,positionerImgName,true);
} else {
  setPosition(elt,positionerImgName)
}
}function toggleDatePicker(eltName,formElt) {
  var x = formElt.indexOf('.');
  var formName = formElt.substring(0,x);
  var formEltName = formElt.substring(x+1);
  newCalendar(eltName,document.forms[formName].elements[formEltName]);
  toggleVisible(eltName);
}
</SCRIPT>
第二步：把如下代码加入到<body>区域中<FORM name=date>
<CENTER>
<TABLE border=1 width=225>
  <TBODY>
  <TR>
    <TD width=89>开始日期: </TD>
    <TD width=120><INPUT name=ret size=10> <IMG align=absMiddle
      alt="date picker" border=0 height=19 id=daysOfMonthPos name=daysOfMonthPos
      onmouseup="toggleDatePicker('daysOfMonth','date.ret')"
      src="../sjrq/images/calendaricon.gif" width=19>
      <DIV id=daysOfMonth style="POSITION: absolute"></DIV></TD></TR>
  <TR>
    <TD width=89>终止日期: </TD>
    <TD width=120><INPUT name=ret2 size=10> <IMG align=absMiddle
      alt="date picker" border=0 height=19 id=daysOfMonth2Pos
      name=daysOfMonth2Pos
      onmouseup="toggleDatePicker('daysOfMonth2','date.ret2')"
      src="../sjrq/images/calendaricon.gif" width=19>
      <DIV id=daysOfMonth2
style="POSITION: absolute"></DIV></TD></TR></TBODY></TABLE></CENTER></FORM>
<P>
<SCRIPT language=JavaScript1.2> function Cancel() {
        hideElement("daysOfMonth");
}</SCRIPT><SCRIPT language=JavaScript1.2>
hideElement('daysOfMonth');
hideElement('daysOfMonth2');
</SCRIPT>

调试易

有三个下拉列表框:年,月,日,我选了年和月之后日的列表框能否自动识别当前月份有多少天??

解决方案 »