Custom Validity
by giacal
HTML
<form>
Password:
<input type="text" name="password" id="password" required><br>
Ripeti password:
<input type="text" name="ripeti_password" id="ripeti_password" required><br>
<input type="submit" id="submit" value="invia">
</form>
JavaScript
var btn=document.querySelector('#submit'),
psw1=document.forms[0].password,
psw2=document.forms[0].ripeti_password;
btn.addEventListener('click',checkPsw, false);
function checkPsw(){
if (psw1.value != psw2.value)
psw1.setCustomValidity("Password diverse!!!");
else
psw1.setCustomValidity("");
}