JSFiddle - React, Tailwind, and code Playground

HTML

<h1>ahh</h1>
<h1 id="whatever">ahh</h1>
<h1>ahh</h1>
<h1>ahh</h1>

JavaScript

var h1s = document.getElementsByTagName("h1");
for (var i = 0; i < h1s.length; i++) {
    var h1 = h1s[i];
    if (!h1.id) {
        h1.id = "h1" + i + (new Date().getTime());
    }
}