Siema - add arrows navigation to prototype

/*Downloaded from https://www.codeseek.co/pawelgrzybek/siema-add-arrows-navigation-to-prototype-yVxmEp */
body {
  width: 100%;
  max-width: 30rem;
  margin: 0 auto;
}

img {
  width: 100%;
}

.siema {
  margin: 1rem 0;
  position: relative;
}

button:nth-of-type(1) {
  position: absolute;
  left: 0;
  top: 50%;
}

button:nth-of-type(2) {
  position: absolute;
  right: 0;
  top: 50%;
}

/*Downloaded from https://www.codeseek.co/pawelgrzybek/siema-add-arrows-navigation-to-prototype-yVxmEp */
// Because this is possible
// It doesn't mean that this is a best solution
// This is a case when you may look at some more complex tools
// Like very cool Flickity or Swiper

var siemas = document.querySelectorAll('.siema');

// Extend prototype with method that adds arrows to DOM
// Style the arrows with CSS or JS — up to you mate
Siema.prototype.addArrows = function () {
  var _this = this;

  // make buttons & append them inside Siema's container
  this.prevArrow = document.createElement('button');
  this.nextArrow = document.createElement('button');
  this.prevArrow.textContent = 'previous slide';
  this.nextArrow.textContent = 'next slide';
  this.selector.appendChild(this.prevArrow);
  this.selector.appendChild(this.nextArrow);

  // event handlers on buttons
  this.prevArrow.addEventListener('click', function () {
    return _this.prev();
  });
  this.nextArrow.addEventListener('click', function () {
    return _this.next();
  });
};

// this is fairly new way of looping through DOM Elements
// More about ithere: https://pawelgrzybek.com/loop-through-a-collection-of-dom-elements/
// For better compatibility I suggest using for loop
var _iteratorNormalCompletion = true;
var _didIteratorError = false;
var _iteratorError = undefined;

try {
  for (var _iterator = siemas[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
    var siema = _step.value;

    var instance = new Siema({
      selector: siema
    });
    instance.addArrows();
  }
} catch (err) {
  _didIteratorError = true;
  _iteratorError = err;
} finally {
  try {
    if (!_iteratorNormalCompletion && _iterator.return) {
      _iterator.return();
    }
  } finally {
    if (_didIteratorError) {
      throw _iteratorError;
    }
  }
}