Accordion无法使用Javascript (无法读取属性)

<div class="accordion">
  <input type="checkbox" id="accordion1" class="accordion-input">
  <label for="accordion1" class="accordion-label">标题1</label>
  <div class="accordion-content">
    内容1
  </div>
  
  <input type="checkbox" id="accordion2" class="accordion-input">
  <label for="accordion2" class="accordion-label">标题2</label>
  <div class="accordion-content">
    内容2
  </div>
  
  <input type="checkbox" id="accordion3" class="accordion-input">
  <label for="accordion3" class="accordion-label">标题3</label>
  <div class="accordion-content">
    内容3
  </div>
</div>

.accordion-input {
  display: none;
}

.accordion-label {
  display: block;
  cursor: pointer;
}

.accordion-content {
  display: none;
}

.accordion-input:checked + .accordion-label + .accordion-content {
  display: block;
}