Auto Fill Field

// ==UserScript==
// @name         Fill in Arnona form 1/4
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        https://city4u.co.il/PortalServicesSite/cityPay/264000/mislaka/1
// @grant        none
// ==/UserScript==

//CcNumber
(function() {
    'use strict';
    fillInField("MisparHeshbon", "xxxxxx");
    fillInField("txtPhone", "xxxxxx");
    fillInField("txtEmail", "xxxx@gmail.com");
    fillInField("txtFullName", "xxxxx");
    fillInField("CcNumber", "xxxxxxx");
    fillInField("ccOwnerId", "xxxxx");
    fillInField("CcValidationCode", "029");
    var yearFieldName = "שנה";
    fillInComboBox(yearFieldName, "0", 0);
    var monthFieldName = "חודש";
    fillInComboBox(monthFieldName, "4", 1);
})();

function fillInField(fieldName, value) {
    (function() {
        var checkExist = setInterval(function() {
            var fieldObj = document.getElementById(fieldName);
            if (fieldObj != null) {
                console.log(fieldName + " exists!");
                fieldObj.value = value;
                clearInterval(checkExist);
            }
        }, 100); // check every 100ms
    })();
}

function fillInComboBox(fieldName, value, index) {
    (function() {
        var checkExist = setInterval(function() {
            var selectField = document.getElementsByClassName("select-cc-date")[index];
            var isField = selectField.innerHTML.includes(fieldName);
            if (isField) {
                console.log(fieldName + " exists!");
                selectField.value = value;
                clearInterval(checkExist);
            }
        }, 100); // check every 100ms
    })();
}