How to refresh/update select in Javascript (vanilla) with Materialize?

Question

I am attempting to update options in a select-widget by using Javascript (vanilla) with Materialize. I have I guess it is related to "dynamically generated select elements", but I am not sure what to do?

According to Materialize I may need to consider to implement: "In addition, you will need a separate call for any dynamically generated select elements your page generates." . Unfortunately, I am not sure (did not found) how I can "dynamically generated select elements" as to update/refresh the select-widget?

Here are my related codes:

HTML

<!--Let browser know website is optimized for mobile-->
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<!--Import Google Icon Font-->
<link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
<!-- Compiled and minified CSS -->
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/materialize/1.0.0/css/materialize.min.css">
<div class = "container">
    <div class="row">
      <div class="input-field col s3">
        <button id = "btn" class="waves-effect waves-light btn-small"><i class="material-icons left">person_add</i>Add</button>
      </div>
      <div class="row">
      <div class="input-field col s3">
        <button id = "btnRemove" class="waves-effect waves-light btn-small"><i class="material-icons left">delete</i>Remove</button>
      </div>
    </div> <!-- CLOSE ROW -->

    <div class="row">
      <div>
        <div style = "position:relative; top:-10px;" class="input-field col s6">
          <select id="voteNoList" onchange="PersonInfo()" required>
            <option value="">Vote Number?</option>
            <!-- <?!= currListNo; ?>
               -->
            <option value="1">Option 1</option>
            <option value="2">Option 2</option>
            <option value="3">Option 3</option>
          </select>
        </div>
      </div>
    </div> <!-- CLOSE ROW -->
</div> <!-- CLOSE CONTAINER -->

Javascript (Vanilla)

  //------------
  // AUTO
  //------------
  // Select
  document.addEventListener('DOMContentLoaded', function() {
    var el = document.querySelectorAll('select');
    var instances = M.FormSelect.init(el);
  });

  // Button - Add
  document.getElementById("btn").addEventListener("click", PersonInfo);

  // Button - Remove
  document.getElementById("btnRemove").addEventListener("click", PersonDelete);

  function PersonInfo(){

    debugger;
    var selectobject = document.createElement("option");
    selectobject.text = "Text55";
    selectobject.value = "myvalue55";
    var selectList = document.getElementById("voteNoList");
    selectList.appendChild(selectobject);  
    debugger;
    return;        
  }

  function PersonDelete(){

    debugger;
    var selectobject=document.getElementById("voteNoList");
    for (var i=0; i<selectobject.length; i++){
      if (selectobject.options[i].value == "2"){
         selectobject.remove(i);
        break;
      }
    } 
    debugger;
    return;     
  }

My expectation was to have a select-widget which can increase and decrease in options depending on how the buttons have been pressed. (Observe that for simplicity, I hard-coded to only be able to add the same option and delete the option that is equal to "2" .)

Although I could not find a solution in Javascript (vanilla), I was able to find a jQuery solution as seen in link .

My codes are also available in CodePen , where one can see in debug mode that the different number options of selectList change when pressing the buttons.

Answer 1

Apparently, the solution to my case was to add M.FormSelect.init(selectList); before return . The codes with the update/solution are available in CodePen .