<main>
  <h2>CSS Animations: the <code>animation-direction</code> Property</h2>

  <p>Use the select box below to set the animation direction. You can also change the iteration count.</p>

  <div class="box">
  </div>
  
  <input id="iteration" type="number" min="0" step="0.1" value="1">
  <select id="direction">
    <option value="normal">normal</option>
    <option value="reverse">reverse</option>
    <option value="alternate">alternate</option>
    <option value="alternate-reverse">alternate-reverse</option>
  </select>

  <br>

  <button>Animate the Box</button> <button disabled>Reset</button>

</main>

body {
  font-family: Arial, sans-serif;
  font-size: 20px;
  padding: 0 20px;
}

main {
  text-align: center;
  margin: 0 auto;
  max-width: 800px;
}

p {
  padding: 0 20px;
}

code {
  color: firebrick;
}

.box {
  width: 100px;
  height: 100px;
  background: orange;
  border: solid 2px;
  margin-bottom: 20px;
}

.box-animate {
  animation-name: moveObject;
  animation-duration: 2s;
}

@keyframes moveObject {
  from {
    transform: translateX(0);
  }

  to {
    transform: translateX(600px);
  }
}

input[type=number] {
  width: 60px;  
}

button {
  margin-top: 20px;
}

console.clear();

let myObject = document.querySelector('.box'),
    btn1 = document.querySelector('button'),
    btn2 = document.querySelectorAll('button')[1],
    iteration = document.querySelector('#iteration'),
    direction = document.querySelector('#direction');

btn1.addEventListener('click', function () {
  myObject.style.animationIterationCount = document.querySelector('#iteration').value;
  myObject.style.animationDirection = document.querySelector('#direction').value;
  myObject.classList.add('box-animate');
  this.disabled = true;
  btn2.disabled = false;
}, false);

btn2.addEventListener('click', function () {
  myObject.classList.remove('box-animate');
  this.disabled = true;
  btn1.disabled = false;
}, false);