JSFiddle - React, Tailwind, and code Playground

HTML

<select name="size" id="shoes-size">
  <option value="33">33</option>
  <option value="34">34</option>
  <option value="35">35</option>
  <option value="inny">inny</option>
</select>

<input type="text" name="different" id="shoes-size-different">

JavaScript

$('#shoes-size-different').hide();

$('#shoes-size').on('change', function(){
	if($(this).val()=='inny'){
  	$('#shoes-size-different').show();
	}
  else{
  	$('#shoes-size-different').hide();
  }
});