JQuery Нормализация номера телефона (приведение к единому формату)

function NormalizePhoneNumber(phone) {
    var normalizePhone = "";
    if (!phone.trim()) return null;
    for (i = 0; i < phone.length; i++) {
        if (!isNaN(parseInt(phone[i]))) {
            normalizePhone += phone[i];
        }
    }
    if (normalizePhone.length == 0 || normalizePhone[0] != "7") {
        normalizePhone = "7" + normalizePhone.substring(1);
    } else {
        normalizePhone = normalizePhone.toString();
    }
    return normalizePhone.length > 11 ? normalizePhone.substring(0, 11) : normalizePhone;