问展开目录的其余部分以显示完整内容(带按钮的onClick)

EN

var coll = document.getElementsByClassName("collapsible");    for (i = 0; i < coll.length; i++) {
  coll[i].addEventListener("click", function() {
    this.classList.toggle("active");
    var content = this.nextElementSibling;

    if (content.style.maxHeight){
      content.style.maxHeight = null;
    } else {
      content.style.maxHeight = content.scrollHeight + "px";
    } 
  });
}

.collapsible {
  background-color: red;
  color: black;
  cursor: pointer;
  padding: 18px;
  width: 100%;
  border: none;
  text-align: left;
  outline: none;
  font-size: 15px;
}


.collapsible:after {
  content: '+';
  color: black;
  float: right;
  margin-left: 5px;
}



.active:after {
  content: "-";
}
.content {
  padding: 0 18px;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0s ease-out;
  text-align: left;
  font-size: 16px;
  line-height: 20px;
  margin-bottom: 15px;
}

<button class="collapsible">Title 1</button>
<div class="content">
  Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
</div>



<button class="collapsible">Title 2 <br>   Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</button>
<div class="content">
  Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
</div>