JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
  <h1>Hi</h1>
  <h2 class="Hi">Test</h2>
  Hi
</div>

JavaScript

var children='';
$('#container').children().each(function(){
    $(this).html($(this).html().replace(/Hi/g,"Hello"));
    children=children+$(this)[0].outerHTML;
});
var theText=$('#container').clone().children().remove().end().text();
$('#container').html('');
$('#container').append(children+theText.replace(/Hi/g,"Hello"));