codice:
<script type="text/javascript" language="javascript">

function checkusername(){
var status = document.getElementById("usernamestatus");
var u = document.getElementById("uname").value;
if(u == 0){
status.innerHTML = "Inserisci un username valido";
} else {
if(u != ""){
status.innerHTML = 'ricerca...';
var hr = new XMLHttpRequest();
hr.open("POST", "controllausr.php", false);
hr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
hr.onreadystatechange = function() {
if(hr.readyState == 4 && hr.status == 200) {
status.innerHTML = hr.responseText;
var oku = hr.responseText;
}
}
    var v = "name2check="+u;
    hr.send(v);
}
}
}

function checkmail(){
var status = document.getElementById("mailstatus");
var u = document.getElementById("mail").value;
if(u == 0){
status.innerHTML = "Inserisci una email valida";
} else {
if(u != ""){
status.innerHTML = 'ricerca...';
var hr = new XMLHttpRequest();
hr.open("POST", "controllamail.php", false);
hr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
hr.onreadystatechange = function() {
if(hr.readyState == 4 && hr.status == 200) {
status.innerHTML = hr.responseText;
var okm = hr.responseText;
}
}
    var v = "mail2check="+u;
    hr.send(v);
}
}
}

bottonereg(oku,okm);

function bottonereg(oku, okm){ 
if ((oku == "Ok")&&(okm == "Ok")){ 
alert("Tentativo riuscito");
} 
}