JSFiddle - React, Tailwind, and code Playground

HTML

<span class="toggler">A</span>
<span class="toggler">B</span>
<span class="toggler">C</span>
<br />
<input type="button" onclick="getToggleClasses()" value="Run inline" />
<input type="button" onclick="getToggleClasses2()" value="Run variable" />
<br />
<div id="results"></div>

JavaScript

function getToggleClasses() {
  var toggler = [],
      elements = document.getElementsByTagName("*"),
      i=0,
      len = elements.length;
    
  for (i; i < len; i++) {
    if (/toggler/g.test(elements[i].className)) {
      toggler.push(elements[i]);
    }
  }
    
  document.getElementById('results').innerHTML += "<br />Inline: " + toggler.length;
}
function getToggleClasses2() {
  var toggler = [],
      elements = document.getElementsByTagName("*"),
      tester = /toggler/g,
      i=0,
      len = elements.length;
    
  for (i; i < len; i++) {
    if (tester.test(elements[i].className)) {
      toggler.push(elements[i]);
    }
  }
    
  document.getElementById('results').innerHTML += "<br />Variable: " + toggler.length;
}