SOURCE

window.addAccordion = function (trigger, content) {
  trigger.addEventListener('click', function () {
    if (content.className.indexOf('accordion-content-show') !== -1) {
      content.className = content.className.replace('accordion-content-show', '')
    } else {
    content.classList.add('accordion-content-show')    
    }
  })    
}
var trigger = document.querySelector('.accordion-title')
var content = document.querySelector('.accordion-content')
addAccordion(trigger, content)

<div class="accordion">
	<div class="accordion-title">标题</div>
  <div class="accordion-content">
  	<div>内容</div>
    <div>内容</div>
    <div>内容</div>
    <div>内容</div>
    <div>内容</div>
  </div>
</div>

.accordion-title {
  box-sizing: border-box;
  background-color: #31b794;
  height: 30px;
  color: #fff;
  line-height: 20px;
  padding: 5px 10px;
  cursor: pointer;
}
.accordion-content {
  box-sizing: border-box;
  border: solid 1px #e6e6e6;
  border-top: none;
  padding: 5px 10px;
  line-height: 1.5;
  transition: all cubic-bezier(0.23, 1, 0.32, 1) 300ms;
  transform: scaleY(0);
  transform-origin: 0 0 0;  
}
.accordion-content-show {
  transform: scaleY(1);
  transform-origin: 0 0 0;
}