JSFiddle - React, Tailwind, and code Playground

HTML

<p>This one works.</p>
<form>
<select name="deliveryType">
    <option value="123">Item 1</option>
    <option value="456">Item 2</option>
    <option value="789">Item 3</option>
  </select>
  <p><a href="javascript:void(0);" onClick="javascript:addToCart(this);">Submit</a>
</form>

<p>This one <u>does not</u> work.</p>
<form><select name="deliveryType">
    <option value="123">Item 1</option>
    <option value="456">Item 2</option>
    <option value="789">Item 3</option>
  </select>
  <p><a href="javascript:void(0);" onClick="javascript:addToCart(this);">Submit</a>
</form>

<script>
      function addToCart(t) {
        var dT = t.parentNode.parentNode.childNodes[1].value;
        alert(dT);
        // location.href = "http://linkprefix.com/?variable=" + dT;
      }</script>