JSFiddle - React, Tailwind, and code Playground

HTML

<script type="text/javascript">
    function setTest(x)
   {
      document.getElementById(x).value = "this is a test value"; 
    }
</script>

   <input type="text" name="test" id="test" size="10" value="lalala"> 
   <button value="FILL"  onClick="if( confirm( 'Are you sure you want to set this field.') ){ setTest('test'); }">