Confirm Password match validation html5

<script>
//confirm password match
var new_password = document.getElementById("new_password")
  , confirm_password = document.getElementById("confirm_password");

function validatePassword(){
  if(new_password.value != confirm_password.value) {
    confirm_password.setCustomValidity("Passwords Don't Match");
  } else {
    confirm_password.setCustomValidity('');
  }
}
new_password.onchange = validatePassword;
confirm_password.onkeyup = validatePassword;
</script>