Calculating age from date of birth in javascript?

[radhika vk]

Hi ,

I am using date of birth field in my application and i m taking date of birth in yyyy-mm-dd format.

I need to calculate age by using this date of birth and should show alert if age is less than 5 years.

help me....

Thanks in advance

[Philip M]

Here you are:-

Enter Date Of Birth in nowyearYY-MM-DD format <input type = "text" name = "dob" id = "dob" size = "10" maxlength = "10" onblur = "checkAge()">

<script type="text/javascript"> 

function checkAge(){ 
var today = new Date(); 
var d = document.getElementById("dob").value;
if (!/\d{4}\-\d{2}\-\d{2}/.test(d)) {   // check valid format
showMessage();
return false;
}

d = d.split("-");
var byr = parseInt(d[0]); 
var nowyear = today.getFullYear();
if (byr >= nowyear || byr < 1900) {  // check valid year
showMessage();
return false;
}
var bmth = parseInt(d[1],10)-1;   // radix 10!
if (bmth <0 || bmth >11) {  // check valid month 0-11
showMessage() 
return false;
}
var bdy = parseInt(d[2],10);   // radix 10!
var dim = daysInMonth(bmth+1,byr);
if (bdy <1 || bdy > dim) {  // check valid date according to month
showMessage();
return false;
}

var age = nowyear - byr;
var nowmonth = today.getMonth();
var nowday = today.getDate();
if (bmth > nowmonth) {age = age - 1}  // next birthday not yet reached
else if (bmth == nowmonth && nowday < bdy) {age = age - 1}

alert('You are ' + age + ' years old'); 
if (age <= 15) {
alert ("You are 15 years old or less!");  
}
}

function showMessage() {
if (document.getElementById("dob").value != "") {
alert ("Invalid date format or impossible year/month/day of birth - please re-enter as nowyearYY-MM-DD");
document.getElementById("dob").value = "";
document.getElementById("dob").focus();
}
}

function daysInMonth(month,year) {  // months are 1-12
var dd = new Date(year, month, 0);
return dd.getDate();
} 

</script>

BTW, the time to say "thanks" is afterwards, not beforehand which gives the - doubtless unintended - impression that you take other people's voluntary unpaid assistance for granted. Or as British politician Neil Kinnock put it, "Don't belch before you have had the meal." Prefer to use "please" beforehand and if you find a response helpful then you can use the "Thank User For This Post" button.


"In the beginner's mind there are many possibilities, but in the expert's mind there are few” - Shunryu Suzuki (Japanese Zen priest, ?-1971)

[crisstina]

Thank you! this script was extremely useful for me...

I just fixed a little thing about the "birthday"... if someone logs in and their birthday is the same day, then the app will allow them to register.

here's the adjusted code:



function checkAge()
{

var today = new Date();
var d = document.getElementById("dob").value;
if (!/\d{4}\-\d{2}\-\d{2}/.test(d))
{ // check valid format
showMessage();
return false;
}

d = d.split("-");
var byr = parseInt(d[0]);
var nowyear = today.getFullYear();
if (byr >= nowyear || byr < 1900)
{ // check valid year
showMessage();
return false;
}
var bmth = parseInt(d[1],10)-1; // radix 10!
if (bmth <0 || bmth >11)
{ // check valid month 0-11
showMessage();
return false;
}
var bdy = parseInt(d[2],10); // radix 10!
var dim = daysInMonth(bmth+1,byr);
if (bdy <1 || bdy > dim)
{ // check valid date according to month
showMessage();
return false;
}

var age = nowyear - byr;
var nowmonth = today.getMonth();
var nowday = today.getDate();
var age_month = nowmonth - bmth;
var age_day = nowday - bdy;
if (age < 18 )
{
alert ("We're sorry but thesite.com won't allow children under 18 years old to login.");
}
else if (age == 18 && age_month <= 0 && age_day <0)
{
alert ("We're sorry but thesite.com won't allow children under 18 years old to login.");
}


}

function showMessage()
{
if (document.getElementById("dob").value != "")
{
alert ("Invalid date format or impossible year/month/day of birth - please re-enter as YYYY-MM-DD");
document.getElementById("dob").value = "";
document.getElementById("dob").focus();
}
}

function daysInMonth(month,year) { // months are 1-12
var dd = new Date(year, month, 0);
return dd.getDate();
}

[instigator2]

I decided to try this script today and it worked very well. Thank you, Phillip M for your contribution and to crisstina for your modification.

Much appreciated