JSFiddle - React, Tailwind, and code Playground

HTML

<!-- componentID: 1234 -->
<div class="some-class"> .... </div>

<!-- componentID: 1235 -->
<div class="another-class"> .... </div>

JavaScript

var x = document.evaluate('//comment()', document, null, XPathResult.ANY_TYPE, null),
    comment = x.iterateNext();

while (comment) {
    alert(comment.textContent);
    comment = x.iterateNext();
}