JSFiddle - React, Tailwind, and code Playground

HTML

<span id="actual-change-to-h1">Hello</span>

JavaScript

var mySpan = document.getElementById("actual-change-to-h1");
var myH1 = document.createElement("h1");
myH1.innerHTML = mySpan.innerHTML;
mySpan.parentNode.replaceChild(myH1, mySpan);