Validate Age

This snippet presupposed an HTML form with and ID of “age-form” and three inputs (text or select) with the IDs “day”, “month”, and “year” respectively.

$("#age-form").submit(function(){
	var day = $("#day").val();
	var month = $("#month").val();
	var year = $("#year").val();
	var age = 18;
	var mydate = new Date();
	mydate.setFullYear(year, month-1, day);

	var currdate = new Date();
	currdate.setFullYear(currdate.getFullYear() - age);
	if ((currdate - mydate) < 0){
		alert("Sorry, only persons over the age of " + age + " may enter this site");
		return false;
	}
	return true;
});

You may wish to do something more elegant than an alert, and should also probably validate the form with server side code or else this protection only works for users with JavaScript enabled.