JSFiddle - React, Tailwind, and code Playground

HTML

<p id="myText" onMouseup="myFunction()">Hello world!</p>

<script>
function myFunction() {
  if (window.getSelection().toString().length > 0 && document.getElementById("myText")) {
    var elem = document.getElementById("myText");
    var str = elem.innerHTML;
    str = str.split("").reverse().join("");
    elem.innerHTML = str;
    elem.id = "myTextReversed";
  }
}
</script>