old_contents: /**
   * @module
   * @export {Function} findChild
   */
  
  /**
   * Find element with specific class name within children, like selector '>'
   *
   * @param {Element} parentElem
   * @param {String} className
   *
   * @return {Element}: first matched child
   */
  export const findChild = (parentElem, className) => {
      const children = parentElem.children;
  
      if (!children) return null;
  
      for (let elem of children) {
          if (elem.className.match(className)) return elem;
      }
  
      return null;
  };
  
new_contents: /**
   * @module
   * @export {Function} findChild
   */
  
  /**
   * Find element with specific class name within children, like selector '>'
   *
   * @param {Element} parentElem
   * @param {String} className
   *
   * @return {Element}: first matched child
   */
  export const findChild = (parentElem, className) => {
      const children = parentElem.children;
  
      let res = null;
  
      if (children) {
          [...children].some(elem => {
              if (elem.className.match(className)) {
                  res = elem;
                  return true;
              }
          });
      }
  
      return res;
  };
  
subject: fix '[Symbol.iterator]' is undefined error