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Robert WynterRobert Wynter 

JavaScript get selected index from dropdown

Using JS to add to a dropdown from Salesforce repeater prefills. This works great, however, when I try to get the selected value when a user selects from the dropdown (tfa_4) and add to a text box (tfa_25), I get undefined. I've tried .selectedIndex -1, +1 and just selectedIndex and sometimes it works but only on one or two selected values and not in the right order

<script type="text/javascript">
    window.onload = document.addEventListener("DOMContentLoaded", function() {
    var option = document.createElement("option");
    option.text = "Select Tour Date";
    var startDate = document.querySelectorAll('[id^=tfa_9]');
    var campaignRepaterID = document.querySelectorAll('[id^=tfa_26]');
    for(var i in startDate){
                   textToWrite = startDate[i].value;
                if (textToWrite) {
                    if (textToWrite.length > 1) {
                        displayTime = textToWrite;
  function getSelectedValue(){    //Gets the index value of the selected event
      var x = document.getElementById("tfa_4").selectedIndex - 1;
      //Finds and sets the event ID
var IDToFind = campaignRepaterID[x].value;
var dd = document.getElementById('tfa_25');
    dd.value = IDToFind;

    // Function to add to the campaign dropdown
        function addToDropdown(text) {
            var x = document.getElementById("tfa_4");//Dropdown field
            var option = document.createElement("option");
            option.text = text;