我想使手风琴的第一个元素将默认打开手风琴

<ul class="accordion">
  <li>
    <h3 class="accordion-title">标题1</h3>
    <div class="accordion-content">
      内容1
    </div>
  </li>
  <li>
    <h3 class="accordion-title">标题2</h3>
    <div class="accordion-content">
      内容2
    </div>
  </li>
  <li>
    <h3 class="accordion-title">标题3</h3>
    <div class="accordion-content">
      内容3
    </div>
  </li>
</ul>

.accordion-title {
  cursor: pointer;
}

.accordion-content {
  display: none;
}

.accordion li:first-child .accordion-content {
  display: block;
}

var accordionTitles = document.querySelectorAll('.accordion-title');

accordionTitles.forEach(function(title) {
  title.addEventListener('click', function() {
    var content = this.nextElementSibling;
    content.style.display = (content.style.display === 'block') ? 'none' : 'block';
  });
});