Ok, this is the code I ended up with (which works, by the way), but I was trying to convert the dates to milliseconds instead (no problem) in the isOfLegalAge() function, and figure out if someone was either exactly 18 or older depending upon the birthdate they entered. and whenever I converted to milliseconds and figured it that way, it was off by around 5 days or so, depending upon how long ago it was.
So I ended up using the method you see here. I know it would be off if the client's time was off anyway, like all client-side scripts, but I enjoy writing this stuff for people that need some client-side solution.
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" >
<head>
<title>isOfLegalAge()</title>
<script type="text/javascript">
<!--
function isDate(mm,dd,yyyy) {
var d = new Date(mm + "/" + dd + "/" + yyyy);
return d.getMonth() + 1 == mm && d.getDate() == dd && d.getFullYear() == yyyy;
}
function isOfLegalAge(mm,dd,yyyy) {
var d = new Date(mm + "/" + dd + "/" + yyyy);
var t = new Date();
var diffYears = t.getFullYear() - d.getFullYear();
var diffMonths = t.getMonth() - d.getMonth();
var diffDays = t.getDate() - d.getDate();
return diffYears > 18 ? true : diffYears > 17 && diffMonths > -1 && diffDays > -1;
}
function validateForm(f) {
var errormsg = "";
var focusfield;
if (!isDate(f.month.options[f.month.selectedIndex].value,f.day.options[f.day.selectedIndex].value,f.year.options[f.year.selectedIndex].value)) {
errormsg += "* Invalid date of birth\n";
if (!focusfield) focusfield = "day";
}
if (!isOfLegalAge(f.month.options[f.month.selectedIndex].value,f.day.options[f.day.selectedIndex].value,f.year.options[f.year.selectedIndex].value)) {
errormsg += "* You must be at least 18 years of age\n";
}
if (errormsg != "") {
alert("The following errors were encountered:\n\n" + errormsg);
if (focusfield) eval('f.' + focusfield + '.focus()');
return false;
}
else {
return true;
}
}
// -->
</script>
</head>
<body>
<form id="dateform" action="birthdate.htm" method="get" onsubmit="return validateForm(this)">
<table>
<tr>
<td>Date of Birth: </td>
<td>
<script type="text/javascript">
//<![CDATA[
/* Get today's date */
var t = new Date();
var mm = t.getMonth();
var dd = t.getDate();
var yyyy = t.getFullYear();
/* Create an array of month names */
var monthnames = new Array("January","February","March","April","May","June","July","August","September","October","November","December");
/* Create month select */
var monthselect = "";
monthselect += '<select name="month">';
for (var i = 0; i < 12; i++) {
monthselect += '<option value="' + (i + 1) + '"';
if (i == mm) {
monthselect += ' selected="selected"';
}
monthselect += '">' + monthnames[i] + '</option>';
}
monthselect += '</select>';
/* Create day select */
var dayselect = "";
dayselect += '<select name="day">';
for (var i = 0; i < 31; i++) {
dayselect += '<option value="' + (i + 1) + '"';
if (i + 1 == dd) {
dayselect += ' selected="selected"';
}
dayselect += '>' + (i + 1) + '</option>';
}
dayselect += '</select>';
/* Create year select */
var yearselect = "";
yearselect += '<select name="year">';
for (var i = yyyy; i > yyyy - 101; i--) {
yearselect += '<option value="' + i + '"';
if (i == yyyy - 18) {
yearselect += ' selected="selected"';
}
yearselect += '>' + i + '</option>';
}
yearselect += '</select>';
/* Write the selects */
document.write(monthselect + dayselect + yearselect);
//]]>
</script>
</td>
</tr>
<tr>
<td colspan="2" align="center">
<input type="submit" value="Submit" />
<input type="reset" value="Reset" />
</td>
</tr>
</table>
</form>
</body>
</html>
P.S. That doesn't necessarily mean there is a "bug" in the date objects, it probably just means that:
<pseudocode>
function snafu() {
return (milliseconds * minutes * hours * days in a year) != (a true year);
}
</pseudocode>
Would always return true...
...but maybe it is a bug. I dunno. I have a very high aptitude for math according to every test I've taken, but I don't really enjoy it much, therefore I don't know as much about it as I should.
I enjoy programming because it's not just math, it's mostly logic. As you can tell, I also enjoy posting verbose messages on the internet. LOL... just kidding. I thought it would be clearer if you saw what I was trying to do in the first place and the solution I ended up with. :eek:
;)