Validating Date of Birth

**tahirjadoon** · May 12, 2004 15:35

I need to validate the DOB selected by the user, user should be 13 years of age (Current date - 13) to complete the information on the page. If the user is not 13 then user will be redirected to an error page. I have written a function (below) but i know there must be a much better way of doing this. Function receives 3 parameters; day, month, and year selected by the user for DOB.

checkDate function called inside the following function checks for the valid date or not.

function CheckDOBforThirteen(nDay,nMonth,nYear){
//if error return true other wise return false
var blnReturn = false;

//get current day, month and year
var strDate = new Date;

var nMonthC = parseInt(strDate.getMonth() + 1);
var nDayC = parseInt(strDate.getDate());
var nYearC = parseInt(strDate.getFullYear());

//change the selected info into date format
var dSelected = new Date(nMonth+"/"+nDay+"/"+nYear);

//Calculate date with current year -13, this might become February 29 and also
//this might not be a leap year, check that we have the valid date 13 years before
//If it is valid keep it, otherwise add 1 to month and make day as 1. It will become
//March 1 then
if(!checkDate(nMonthC+"/"+nDayC+"/"+(nYearC - 13)))
var dThirteen = new Date(nMonthC+1+"/1/"+(nYearC - 13));
else
var dThirteen = new Date(nMonthC+"/"+nDayC+"/"+(nYearC - 13));

if(dSelected > dThirteen)
blnReturn = true;

return blnReturn;
}

**adios** · May 12, 2004 20:21

Probably helps to filter your input with drop-downs.
Note: the document.write()s are for abbreviating this demo (probably want to hardcode the options in your own form).

Code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 
<html> 
<head> 
<title>untitled</title> 
<script type="text/javascript"> 

var numDays = {
                '1': 31, '2': 28, '3': 31, '4': 30, '5': 31, '6': 30, 
                '7': 31, '8': 31, '9': 30, '10': 31, '11': 30, '12': 31
              }; 

function setDays(oMonthSel, oDaysSel, oYearSel)
{ 
	var nDays, oDaysSelLgth, opt, i = 1; 
	nDays = numDays[oMonthSel[oMonthSel.selectedIndex].value]; 
	if (nDays == 28 && oYearSel[oYearSel.selectedIndex].value % 4 == 0) 
		++nDays; 
	oDaysSelLgth = oDaysSel.length; 
	if (nDays != oDaysSelLgth)
	{ 
		if (nDays < oDaysSelLgth) 
			oDaysSel.length = nDays; 
		else for (i; i < nDays - oDaysSelLgth + 1; i++)
		{ 
			opt = new Option(oDaysSelLgth + i, oDaysSelLgth + i); 
			oDaysSel.options[oDaysSel.length] = opt;
		} 
	} 
} 

function chkDOB(oMonthSel, oDaysSel, oYearSel)
{
	var DOB = [
	oMonthSel.options[oMonthSel.selectedIndex].text ,
	oDaysSel.options[oDaysSel.selectedIndex].text,
	oYearSel.options[oYearSel.selectedIndex].text
		  ];
	DOB = new Date(DOB.join(', ')).getTime(); //milliseconds in DOB
	var now = new Date().getTime(); //milliseconds in today's date
	var milliday = (24 * 60 * 60 * 1000); //milliseconds in one day
	if ((now - DOB) < ((13 * 365 * milliday) + (4 * milliday))) //compensate for leap year
	{
		self.location = 'http://www.drtill.de/wkwh/die1/images/funpictures/underage.gif'; //redirect
		return false;
	}
	else return true;
}

</script> 
</head> 
<body> 
<form action="javascript&#58;alert('old enough')" method="post" onsubmit="return chkDOB(month,day,year)">
<strong>My date of birth was </strong>
<select name="month" id="month" onchange="setDays(this,day,year)"> 
<option value="1" selected="selected">January</option> 
<option value="2">February</option> 
<option value="3">March</option> 
<option value="4">April</option> 
<option value="5">May</option> 
<option value="6">June</option> 
<option value="7">July</option> 
<option value="8">August</option> 
<option value="9">September</option> 
<option value="10">October</option> 
<option value="11">November</option> 
<option value="12">December</option> 
</select> 
<select name="day" id="day">
<option value="1" selected="selected">1</option>
<script type="text/javascript">
var d = 1;
while (++d < 32)
	document.write('<option value="' + d + '">' + d + '</option>');
</script>
</select> 
<select name="year" id="year" onchange="setDays(month,day,this)">
<script type="text/javascript">
var y = 1939;
while (++y < 2003)
	document.write('<option value="' + y + '">' + y + '</option>');
</script>
<option value="2003" selected="selected">2003</option>
</select>
<input type="submit" value="next" /> 
</form> 
</body> 
</html>

**stereofrog** · May 13, 2004 03:47

tahirjadoon

this can be done in a more elegant way with OOP. Let's add a new method to the Date object, which returns the age:

Code:

<script>

// getAge
// caclucates the age in years from birth date
// usage: birthDate.getAge()

Date.prototype.getAge=function(){
	var today=new Date();
	var years=today.getFullYear()-this.getFullYear()-1;
	if(this.getMonth()>today.getMonth())
		return years;
	if(this.getMonth()<today.getMonth() || this.getDate()<=today.getDate())
		return years+1;
	return years;
}
</script>

Now you can utilize this method to check if user is older than 13:

Code:

<script>
function checkAge(strBirthDate){
	var birthdate=new Date(strBirthDate);
	var age=birthdate.getAge();
	var message="Birthdate: "+birthdate;
	message+="\n you are now "+age+" years old";
	if(age<13)
		message+="\n too young, sorry";
	else
		message+="\n it's ok";
	alert(message);
}
</script>

<h1>Lets test</h1>

Birth date in mm/dd/yyyy format:
<input name=birthdate onblur="checkAge(this.value)" value="5/13/1991">

**tahirjadoon** · May 13, 2004 10:53

below is the modified function.

function CheckDOBforThirteen( nDay, nMonth, nYear ){
var cDate = new Date( nYear + 13, nMonth -1, nDay );
return new Date().getTime() <= cDate.getTime();
}

User Tag List

Thread: Validating Date of Birth

Thread Tools

Display

Validating Date of Birth

Bookmarks

Bookmarks

Posting Permissions