JSFiddle - React, Tailwind, and code Playground
by thecoz21
HTML
<form>
Password: <input type="password" name="password" required><br/>
Ripeti password: <input type="password" name="ripeti_password"><br/>
<input type="submit" id="submit" value="invia">
</form>
JavaScript
var i1 = document.querySelector('input[name=password]'),
su = document.querySelector('#submit'),
i2 = document.querySelector('input[name=ripeti_password]');
su.addEventListener('click', function(){
if(i1.value != i2.value){
i1.setCustomValidity('Le password non coincidono');
}else{
i1.setCustomValidity('');
}
}, false);