function newGuid(){
    var guid = "{";
    for (var i=1; i<=32; i++){
        var n = Math.floor(Math.random()*16.0).toString(16);
        guid +=   n;
        if((i==8)||(i==12)||(i==16)||(i==20))
            guid += "-";
    }
    return guid+"}";
}

=> {d2c37006-4650-189a-f604-034d91371a1a}"