JSFiddle - React, Tailwind, and code Playground

HTML

<div class="outclass classic class">
    <div>
        <div id="element"></div>
    </div>
</div>

JavaScript

function hasClass(element, className) {
  var regex = new RegExp('\\b' + className + '\\b');
  do {
    if (regex.exec(element.className)) {
      return true;
    }
    element = element.parentNode;
  } while (element);
  return false;
}

function hasClass2(element, className) {
  do {
    if (element.classList && element.classList.contains(className)) {
      return true;
    }
    element = element.parentNode;
  } while (element);
  return false;
}

var result = hasClass(document.getElementById('element'), 'class') + " " + hasClass2(document.getElementById('element'), 'class')

alert(result);