var vodafone  = Array (608, 771, 772, 773, 774, 775, 776, 777, 778, 779);
var o2        = Array (601, 602, 606, 607, 720, 721, 722, 723, 724, 725, 726, 727, 728, 729);

function Operator () {
 var cislo = document.getElementById('sms_prijemce').value;
 
 var cas = new Date().getTime();
 
 if (cislo.length > 7) {
  var prvnitri = cislo.substring(0, 3);
  
  document.getElementById('sms_operator').value = 'tmobile';
  document.getElementById('img_captcha').src = './sms.php?captcha=tmobile&' + cas;
  document.getElementById('odesilatel').style.visibility = "hidden";
  document.getElementById('captcha').style.visibility = "visible";
  
  if (in_array(prvnitri, vodafone)) {
    document.getElementById('sms_operator').value = 'vodafone';
    document.getElementById('img_captcha').src = './sms.php?captcha=vodafone&' + cas;
     document.getElementById('odesilatel').style.visibility = "visible";
  } 
  
  if (in_array(prvnitri, o2)) {
    document.getElementById('sms_operator').value = 'o2';
    document.getElementById('img_captcha').src = './sms.php?captcha=o2';
     document.getElementById('odesilatel').style.visibility = "hidden";
     document.getElementById('captcha').style.visibility = "hidden";
  } 
 }
}

function imposeMaxLength(Object, MaxLen) {
  return (Object.value.length <= MaxLen);
}

function in_array (needle, haystack, argStrict) {
    var key = '', strict = !!argStrict;

    if (strict) {
        for (key in haystack) {
            if (parseInt(haystack[key]) === parseInt(needle)) {
                return true;
            }
        }
    } else {
        for (key in haystack) {
            if (parseInt(haystack[key]) == parseInt(needle)) {
              
                return true;
            }
        }
    }

    return false;
}