Validasi Number Telp On JS

<script language = "Javascript">
var digits = "0123456789";
var phoneNumberDelimiters = "()- ";
var validWorldPhoneChars = phoneNumberDelimiters + "+";
var minDigitsInIPhoneNumber = 10;
function isInteger(s)
{   var i;
    for (i = 0; i < s.length; i++)
    {
       var c = s.charAt(i);
        if (((c < "0") || (c > "9"))) return false;
    }
   return true;
}
function trim(s)
{   var i;
    var returnString = "";

    for (i = 0; i < s.length; i++)
    {
        var c = s.charAt(i);
        if (c != " ") returnString += c;
    }
    return returnString;
}
function stripCharsInBag(s, bag)
{   var i;
    var returnString = "";

    for (i = 0; i < s.length; i++)
    {
        var c = s.charAt(i);
        if (bag.indexOf(c) == -1) returnString += c;
    }
    return returnString;
}

function checkInternationalPhone(strPhone){
var bracket=3
strPhone=trim(strPhone)
if(strPhone.indexOf("+")>1) return false
if(strPhone.indexOf("-")!=-1)bracket=bracket+1
if(strPhone.indexOf("(")!=-1 && strPhone.indexOf("(")>bracket)return false
var brchr=strPhone.indexOf("(")
if(strPhone.indexOf("(")!=-1 && strPhone.charAt(brchr+2)!=")")return false
if(strPhone.indexOf("(")==-1 && strPhone.indexOf(")")!=-1)return false
s=stripCharsInBag(strPhone,validWorldPhoneChars);
return (isInteger(s) && s.length >= minDigitsInIPhoneNumber);
}

function ValidateForm(){
    var Phone=document.frmSample.txtPhone

    if ((Phone.value==null)||(Phone.value=="")){
        alert("Please Enter your Phone Number")
        Phone.focus()
        return false
    }
    if (checkInternationalPhone(Phone.value)==false){
        alert("Please Enter a Valid Phone Number")
        Phone.value=""
        Phone.focus()
        return false
    }
    return true
 }
</script>