Votre date de naissance: 

Il existe une version plus récente de cette page qui utilise davantage les fonctionnalités nouvelles de HTML 5.

Le code suivant figure dans l'en-tête du document :

<script type="text/javascript">

function countdown(year, month, day) {
var temp; 
	var future = new Date(year, month-1, day);
	var today = new Date();
	temp= Math.floor((future.getTime() - today.getTime()) /(24*60*60*1000)) + 1;
	if (temp < 0) { temp = temp + 365; }
	return temp;
	
function age(year, month, day) {
	var today = new Date();
	var current_year = today.getFullYear();
	nb_years = current_year - year;
	var had_birthday = (today >= new Date(current_year, month -1, day));
	temp = had_birthday ? nb_years : nb_years -1; // if the birthday is over we remove 1 year
	return temp;
	}
	
function check_text(entry) {
	var temp;
	var exp = new RegExp(/^[0-9]{2}\/[0-9]{2}\/[0-9]{4}$/);
	temp = exp.test(entry);
	if (temp == false) { age_block.innerHTML = "Date invalide.";}
	return temp;
	}
		
function check_date(year, month, day) {
	var temp;
	var newDate = new Date(year, month-1, day); //  we try to generate the date
	if (newDate.getFullYear()  ==  year && newDate.getMonth()  ==  month-1 && newDate.getDate() == day) { temp = true; }
	else { age_block.innerHTML = "Cette date n'existe pas."; temp = false; }
	return temp;
	}
	
function result() {
	var temp;
	var year; var month; var day;
	
	// ancien format dd/mm/yyyy ou dd / mm / yyyy
	var birthday_date = date.value.replace(/ /g, ''); 
	date_valid = check_text(birthday_date);	
	if (date_valid) {
		temp = birthday_date.split('/');
		year = temp[2]; month = temp[1]; day = temp[0]; 
		date_valid = check_date(year, month, day);
		if (date_valid) {
			age_block.innerHTML = "Vous avez " + age(year, month, day) + " ans.";
			var today = new Date();
			var wait = countdown(today.getFullYear(), month, day);
			if (wait == 0) { 
				birthday_block.innerHTML ='
' + image_with_caption(image_name, image_width, image_height, image_caption) + '

Bon anniversaire. 
';
				setTimeout(anime, 2200); 	
				clearTimeout(anime);
				}
			else { birthday_block.innerHTML = "
Il reste " +  wait +  " jours avant votre anniversaire."; }
			}	
		}
	} 
	
</script>

Le code suivant figure dans le corps du document : 

<form id = "form_test_id" onsubmit = "result(); return false;">  
<label for="date_id">Votre date de naissance: </label><input type="text" id="date_id" maxlength="10" value="DD/MM/YYYY" required><br>
<br>
<input type='button' value="Validation" onclick = "result();">  
</form>
<div id="age_block_id"></div>
<div id="birthday_block_id"></div>

<script type="text/javascript">
/* these constants must be initialized after the page is displayed */
const age_block = document.getElementById('age_block_id');
const birthday_block = document.getElementById('birthday_block_id');
const date = document.getElementById('date_id');
</script>