var xmlhttp;

function verificaLogin(){
    doc=document.facaParteForm;
    var login = doc.login.value;
    xmlhttp=GetXmlHttpObject();
    if (xmlhttp==null){
        alert ("Your browser does not support AJAX!");
        return;
    }
    
    var url="inc/verifica_login.php";
    url=url+"?login="+login;
    xmlhttp.onreadystatechange=stateChangedLogin;
    xmlhttp.open("GET",url,true);
    xmlhttp.send(null);
    return false;
}

function stateChangedLogin(){
    if(xmlhttp.readyState==3){
        alert('Verificando Usuário');
    }
    if(xmlhttp.readyState==4){
        if(xmlhttp.responseText == "1"){
            alert('Usuário já cadastrado. Utilize outro Login.');
            document.facaParteForm.login.focus();
            return false;
        }
    }
}

function GetXmlHttpObject(){
    if (window.XMLHttpRequest){
        // code for IE7+, Firefox, Chrome, Opera, Safari
        return new XMLHttpRequest();
    }
    if (window.ActiveXObject){
        // code for IE6, IE5
        return new ActiveXObject("Microsoft.XMLHTTP");
    }
    return null;
}