// JavaScript Document

function validateFormOnSubmit() {
var reason = "";

  
  reason += validateIMEI(document.getElementById('imei'));
  
      
  if (reason != "") {
    alert("IMEI Error:\n" + reason);
    return false;
  }

  return true;
}
function validateIMEI(fld) {
    var error = "";
    var stripped = fld.value.replace(/[\(\)\.\-\ ]/g, '');    

   if (fld.value == "") {
        error = "Please Enter Your Phones IMEI.\nThen CLICK Update Cart\n";
        fld.style.background = 'Yellow';
    } else if (isNaN(parseInt(stripped))) {
        error = "Please Enter IMEI numbers only, no slashes or lines.\nThen CLICK Update Cart\n";
        fld.style.background = 'Yellow';
    } else if (!(stripped.length == 15)) {
        error = "Your IMEI is an incorrect length please double check.\n";
        fld.style.background = 'Yellow';
    }
	if (error=="") {
	if(!isIMEI(stripped)){
	error = "Your IMEI is INVALID, Please double check against your phone \nBy Entering *#06#.\nThen CLICK Update Cart\n";
	fld.style.background = 'Yellow';
	}
	}
    return error;
}
function isIMEI (s) {
var etal = /^[0-9]{15}$/;
  if (!etal.test(s))
    return false;
  sum = 0; mul = 2; l = 14;
  for (i = 0; i < l; i++) {
    digit = s.substring(l-i-1,l-i);
    tp = parseInt(digit,10)*mul;
    if (tp >= 10)
         sum += (tp % 10) +1;
    else
         sum += tp;
    if (mul == 1)
         mul++;
    else
         mul--;
    }
  chk = ((10 - (sum % 10)) % 10);
  if (chk != parseInt(s.substring(14,15),10))
    return false;
  return true;
}