var getElementsByClassName = function(className) {
  var listArray = [];

  // START INNER FUNCTION
  var innerFn = function(node) {
    if (node.nodeType === 1) {
      if (node.classList.value.includes(className)) {
        listArray.push(node);
      }
    }
    node.childNodes.forEach( function(element) {
      return innerFn(element);
    });
  };
  // END INNER FUNCTION
  
  innerFn(document.body);
  return listArray;
};