// Declaring required variables
var digits = "0123456789";
// non-digit characters which are allowed in phone numbers
var phoneNumberDelimiters = "()- ";
// characters which are allowed in international phone numbers
// (a leading + is OK)
var validWorldPhoneChars = phoneNumberDelimiters + "+";
// Minimum no of digits in an international phone no.
var minDigitsInIPhoneNumber = 7;

function isInteger(s) {
    var i;
    for (i = 0; i < s.length; i++) {
        // Check that current character is number.
        var c = s.charAt(i);
        if (((c < "0") || (c > "9"))) return false;
    }
    // All characters are numbers.
    return true;
}

function stripCharsInBag(s, bag) {
    var i;
    var returnString = "";
    // Search through string's characters one by one.
    // If character is not in bag, append to returnString.
    for (i = 0; i < s.length; i++) {
        // Check that current character isn't whitespace.
        var c = s.charAt(i);
        if (bag.indexOf(c) == -1) returnString += c;
    }
    return returnString;
}

function checkInternationalPhone(strPhone) {
    s = stripCharsInBag(strPhone, validWorldPhoneChars);
    return (isInteger(s) && s.length >= minDigitsInIPhoneNumber);
}


function checkFields(thisForm) {

    missinginfo = "";

    if ((thisForm.email.value <= 0) ||
(thisForm.email.value.indexOf('@') == -1) ||
(thisForm.email.value.indexOf('.') == -1)) {
        missinginfo += "\n     -  Email Address";
    }

    if (missinginfo != "") {
        missinginfo = "Please enter a valid email address";
        alert(missinginfo);
        return false;
    }
    else return true;
}

function clearForm() {
    emailaddress = document.getElementById('maillist_input').value;
    if (emailaddress == "Your Email") {
        document.getElementById('maillist_input').value = "";
    }
}