JSFiddle - React, Tailwind, and code Playground

HTML

<div id="my_example_id" class="ShinyClass">
   My important text
   <span> Here</span>
</div>

<div id="my_example_id" class="ShinyClass">
  
</div>

JavaScript

function getHtml(selector) {
	var element = document.querySelector(selector)
  var htmlText = element.outerHTML
  var start  = htmlText.search(/</)
  var end  = htmlText.search(/>/)
  return htmlText.substr(start, end + 1)
}
alert(getHtml('.ShinyClass'))