Date validation between two date and not greater then 2 from start date

I have two date input boxes Start ans End date. The end date cannot be earlier then the start date also the end date cannot be greater then 24 months from start date .  I found this code in the forums that validates as well as formats, so i would like to try to keep it.
<HEAD>
 
<SCRIPT LANGUAGE="JavaScript">
<!-- Original:  Mike Welagen (welagenm@hotmail.com) -->
 
<!-- This script and many more are available free online at -->
<!-- The JavaScript Source!! http://javascript.internet.com -->
 
<!-- Begin
function checkdate(objName) {
var datefield = objName;
if (chkdate(objName) == false) {
datefield.select();
alert("That date is invalid.  Please try again.");
datefield.focus();
return false;
}
else {
return true;
   }
}
function chkdate(objName) {
var strDatestyle = "US"; //United States date style
//var strDatestyle = "EU";  //European date style
var strDate;
var strDateArray;
var strDay;
var strMonth;
var strYear;
var intday;
var intMonth;
var intYear;
var booFound = false;
var datefield = objName;
var strSeparatorArray = new Array("-"," ","/",".");
var intElementNr;
var err = 0;
var strMonthArray = new Array(12);
strMonthArray[0] = "Jan";
strMonthArray[1] = "Feb";
strMonthArray[2] = "Mar";
strMonthArray[3] = "Apr";
strMonthArray[4] = "May";
strMonthArray[5] = "Jun";
strMonthArray[6] = "Jul";
strMonthArray[7] = "Aug";
strMonthArray[8] = "Sep";
strMonthArray[9] = "Oct";
strMonthArray[10] = "Nov";
strMonthArray[11] = "Dec";
strDate = datefield.value;
if (strDate.length < 1) {
return true;
}
for (intElementNr = 0; intElementNr < strSeparatorArray.length; intElementNr++) {
if (strDate.indexOf(strSeparatorArray[intElementNr]) != -1) {
strDateArray = strDate.split(strSeparatorArray[intElementNr]);
if (strDateArray.length != 3) {
err = 1;
return false;
}
else {
strDay = strDateArray[0];
strMonth = strDateArray[1];
strYear = strDateArray[2];
}
booFound = true;
   }
}
if (booFound == false) {
if (strDate.length>5) {
strDay = strDate.substr(0, 2);
strMonth = strDate.substr(2, 2);
strYear = strDate.substr(4);
   }
}
if (strYear.length == 2) {
strYear = '20' + strYear;
}
// US style
if (strDatestyle == "US") {
strTemp = strDay;
strDay = strMonth;
strMonth = strTemp;
}
intday = parseInt(strDay, 10);
if (isNaN(intday)) {
err = 2;
return false;
}
intMonth = parseInt(strMonth, 10);
if (isNaN(intMonth)) {
for (i = 0;i<12;i++) {
if (strMonth.toUpperCase() == strMonthArray[i].toUpperCase()) {
intMonth = i+1;
strMonth = strMonthArray[i];
i = 12;
   }
}
if (isNaN(intMonth)) {
err = 3;
return false;
   }
}
intYear = parseInt(strYear, 10);
if (isNaN(intYear)) {
err = 4;
return false;
}
if (intMonth>12 || intMonth<1) {
err = 5;
return false;
}
if ((intMonth == 1 || intMonth == 3 || intMonth == 5 || intMonth == 7 || intMonth == 8 || intMonth == 10 || intMonth == 12) && (intday > 31 || intday < 1)) {
err = 6;
return false;
}
if ((intMonth == 4 || intMonth == 6 || intMonth == 9 || intMonth == 11) && (intday > 30 || intday < 1)) {
err = 7;
return false;
}
if (intMonth == 2) {
if (intday < 1) {
err = 8;
return false;
}
if (LeapYear(intYear) == true) {
if (intday > 29) {
err = 9;
return false;
}
}
else {
if (intday > 28) {
err = 10;
return false;
}
}
}
if (strDatestyle == "US") {
datefield.value = strMonthArray[intMonth-1] + " " + intday+" " + strYear;
}
else {
datefield.value = intday + " " + strMonthArray[intMonth-1] + " " + strYear;
}
return true;
}
function LeapYear(intYear) {
if (intYear % 100 == 0) {
if (intYear % 400 == 0) { return true; }
}
else {
if ((intYear % 4) == 0) { return true; }
}
return false;
}
function doDateCheckStarting(start_date, end_date) {
if (Date.parse(start_date.value) <= Date.parse(end_date.value)) {
alert("Dates are good.");
}
else {
if (start_date.value == "" || end_date.value == "")
alert("Start date and End Date must be entered.");
else
alert("Start date must occur before the End Date .");
   }
}
//  End -->
</script>
</HEAD>
 
<!-- STEP TWO: Copy this code into the BODY of your HTML document  -->
 
<BODY>
 
<center>
<form>
<pre>
Start Date <input type=text name=start_date onBlur="checkdate(this)" size=11 maxlength=11 id="start_date">
End Date  <input type=text name=end_date   onBlur="checkdate(this)" size=11 maxlength=11 id="end_date">
 
<input type=button name=formatbutton onClick="doDateCheckStarting(this.form.start_date, this.form.end_date)" value="Check">
</pre>
</form>
</center>

Open in new window

UpperdeckerAsked:
Who is Participating?
 
Lolly-InkConnect With a Mentor Commented:
Modifications:
1. Line 30 - initialised strYear.
2. function doDateCheckStarting - check for > 2 year difference

<html>
<HEAD>
 
<SCRIPT LANGUAGE="JavaScript">
<!-- Original:  Mike Welagen (welagenm@hotmail.com) -->
 
<!-- This script and many more are available free online at -->
<!-- The JavaScript Source!! http://javascript.internet.com -->
 
<!-- Begin
function checkdate(objName) {
var datefield = objName;
if (chkdate(objName) == false) {
datefield.select();
alert("That date is invalid.  Please try again.");
datefield.focus();
return false;
}
else {
return true;
   }
}
function chkdate(objName) {
var strDatestyle = "US"; //United States date style
//var strDatestyle = "EU";  //European date style
var strDate;
var strDateArray;
var strDay;
var strMonth;
var strYear = "";
var intday;
var intMonth;
var intYear;
var booFound = false;
var datefield = objName;
var strSeparatorArray = new Array("-"," ","/",".");
var intElementNr;
var err = 0;
var strMonthArray = new Array(12);
strMonthArray[0] = "Jan";
strMonthArray[1] = "Feb";
strMonthArray[2] = "Mar";
strMonthArray[3] = "Apr";
strMonthArray[4] = "May";
strMonthArray[5] = "Jun";
strMonthArray[6] = "Jul";
strMonthArray[7] = "Aug";
strMonthArray[8] = "Sep";
strMonthArray[9] = "Oct";
strMonthArray[10] = "Nov";
strMonthArray[11] = "Dec";
strDate = datefield.value;
if (strDate.length < 1) {
return true;
}
for (intElementNr = 0; intElementNr < strSeparatorArray.length; intElementNr++) {
if (strDate.indexOf(strSeparatorArray[intElementNr]) != -1) {
strDateArray = strDate.split(strSeparatorArray[intElementNr]);
if (strDateArray.length != 3) {
err = 1;
return false;
}
else {
strDay = strDateArray[0];
strMonth = strDateArray[1];
strYear = strDateArray[2];
}
booFound = true;
   }
}
if (booFound == false) {
if (strDate.length>5) {
strDay = strDate.substr(0, 2);
strMonth = strDate.substr(2, 2);
strYear = strDate.substr(4);
   }
}
if (strYear.length == 2) {
strYear = '20' + strYear;
}
// US style
if (strDatestyle == "US") {
strTemp = strDay;
strDay = strMonth;
strMonth = strTemp;
}
intday = parseInt(strDay, 10);
if (isNaN(intday)) {
err = 2;
return false;
}
intMonth = parseInt(strMonth, 10);
if (isNaN(intMonth)) {
for (i = 0;i<12;i++) {
if (strMonth.toUpperCase() == strMonthArray[i].toUpperCase()) {
intMonth = i+1;
strMonth = strMonthArray[i];
i = 12;
   }
}
if (isNaN(intMonth)) {
err = 3;
return false;
   }
}
intYear = parseInt(strYear, 10);
if (isNaN(intYear)) {
err = 4;
return false;
}
if (intMonth>12 || intMonth<1) {
err = 5;
return false;
}
if ((intMonth == 1 || intMonth == 3 || intMonth == 5 || intMonth == 7 || intMonth == 8 || intMonth == 10 || intMonth == 12) && (intday > 31 || intday < 1)) {
err = 6;
return false;
}
if ((intMonth == 4 || intMonth == 6 || intMonth == 9 || intMonth == 11) && (intday > 30 || intday < 1)) {
err = 7;
return false;
}
if (intMonth == 2) {
if (intday < 1) {
err = 8;
return false;
}
if (LeapYear(intYear) == true) {
if (intday > 29) {
err = 9;
return false;
}
}
else {
if (intday > 28) {
err = 10;
return false;
}
}
}
if (strDatestyle == "US") {
datefield.value = strMonthArray[intMonth-1] + " " + intday+" " + strYear;
}
else {
datefield.value = intday + " " + strMonthArray[intMonth-1] + " " + strYear;
}
return true;
}
function LeapYear(intYear) {
if (intYear % 100 == 0) {
if (intYear % 400 == 0) { return true; }
}
else {
if ((intYear % 4) == 0) { return true; }
}
return false;
}
function doDateCheckStarting(start_date, end_date) {
if (Date.parse(start_date.value) <= Date.parse(end_date.value)) {
   if ((Date.parse(end_date.value) - Date.parse(start_date.value)) > (2 * 365 * 24 * 60 * 60 * 1000))
   {
      alert("End Date is more than 24 months after Start Date.");
   }
   else
   {
      alert("Dates are good.");
   }
}
else {
if (start_date.value == "" || end_date.value == "")
alert("Start date and End Date must be entered.");
else
alert("Start date must occur before the End Date .");
   }
}
//  End -->
</script>
</HEAD>
 
<!-- STEP TWO: Copy this code into the BODY of your HTML document  -->
 
<BODY>
 
<center>
<form>
<pre>
Start Date <input type=text name=start_date onBlur="checkdate(this)" size=11 maxlength=11 id="start_date">
End Date  <input type=text name=end_date   onBlur="checkdate(this)" size=11 maxlength=11 id="end_date">
 
<input type=button name=formatbutton onClick="doDateCheckStarting(this.form.start_date, this.form.end_date)" value="Check">
</pre>
</form>
</center>
   
</body>
</html>

Open in new window

0
 
UpperdeckerAuthor Commented:
So are you saying on line 30 I should

var strYear > "2";
0
 
Lolly-InkCommented:
I initialised the variable strYear as a string because it is possible that a user can enter an invalid date (such as "1") and you would have got a JavaScript error when attempting to access strYear.length when strYear is not a string yet.
0
 
UpperdeckerAuthor Commented:
Thanks
0
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