JSFiddle - React, Tailwind, and code Playground

HTML

<form class="creation">
<select name="select01" class="select01">
     <option value="01">01</option>
     <option value="02">02</option>
     <option value="03">03</option>
</select>

<select name="select02" class="select02" >
     <option value="aa">aa</option>
     <option value="bb">bb</option>
     <option value="cc">cc</option>
</select>
</form>

JavaScript

var el1=document.getElementsByName('select01')[0];
var el2=document.getElementsByName('select02')[0];
el1.onchange = function() {el2.disabled=true;};
el2.onchange = function() {el1.disabled=true;};