JSFiddle - React, Tailwind, and code Playground

HTML

<select id="mySelect">
  <option value="-1">-Select me-</option>
  <option value="1">I'm First</option>
  <option value="2">Oh Second</option>
</select>
<br/>
<br/>

<p id="num-1">
  1111111
</p>
<p id="num-2">
  22222222
</p>
<input type="number" id="myNum" />

JavaScript

$(document).ready(function() {
  $("#mySelect").change(function() {
    var selOption = $(this).val();
    $("#myNum").val(parseInt($("#num-" + selOption).text()));
  });
});