如何在页面加载时保持手风琴面板打开，但之后又保持其可折叠性？

Question

对于我的手风琴菜单，我很难尝试找出如何在加载浏览器时使我的手风琴面板保持打开状态。我试着消除​​overflow：hidden;面板，但我遇到了错误。我希望能够在加载浏览器时打开面板，但是之后让用户打开/关闭链接。

HTML

<div class="sideMenu">
 <div class="logo">TS<div>
 <div class="smallSpacer"></div>

  <div class="accordion">code</div>
   <div class="panel">
    <p>uhn redesign </p>
    <p>180 websites </p>
 </div>

 <div class="bigSpacer"></div>

 <div class="accordion">design</div>
   <div class="panel">
    <p>gigloo </p>
    <p>space is the place</p>
    <p>tyler the creator </p>
    <p>nike concepts</p>
    <p>portraits/fashion</p>
 </div>

 <div class="bigSpacer"></div>

<div class="accordion">personal</div>
   <div class="panel">
    <p>product</p>
    <p>animations</p>
    <p>comics</p>

  </div>
</div>

CSS

body{
font-family: 'Roboto Mono', monospace;
}
.sideMenu{
 background-color:black;
width:250px;
height:100%;
position:fixed;
margin:20px;
text-align:center;
 }
.logo{
 color:white;
}

.smallSpacer{
 margin-bottom:15px;
}

.bigSpacer{
margin-bottom:20px;
}
.accordion {
color: white;
 cursor: pointer;
transition: 0.4s;
font-weight:500;
}

.active, .accordion:hover {

}

.panel {
font-weight:300;
 max-height: 0;
overflow: hidden;
transition: max-height 0.1s ease-out;
}

JAVASCRIPT

var acc = document.getElementsByClassName("accordion");
var i;

for (i = 0; i < acc.length; i++) {
 acc[i].addEventListener("click", function() {
this.classList.toggle("active");
var panel = this.nextElementSibling;
if (panel.style.maxHeight) {
  panel.style.maxHeight = null;
} else {
  panel.style.maxHeight = panel.scrollHeight + "px";
 }
 });
}

这是我的Codepen。 https://codepen.io/taniasharma98/pen/KKwQXBK

Answer 1

这是我的解决方案：

var acc = document.getElementsByClassName("accordion");
var i;

for (i = 0; i < acc.length; i++) {
//this is where magic happens
  if(i==0){
    acc[0].classList.toggle("active");
    var panel = acc[0].nextElementSibling;
    if (panel.style.maxHeight) {
      panel.style.maxHeight = null;
    } else {
      panel.style.maxHeight = panel.scrollHeight + "px";
    }
  }  

  acc[i].addEventListener("click", function() {
    this.classList.toggle("active");
    var panel = this.nextElementSibling;
    if (panel.style.maxHeight) {
      panel.style.maxHeight = null;
    } else {
      panel.style.maxHeight = panel.scrollHeight + "px";
    }
  });
}

如您所见，我所做的就是将手风琴扩展到第一个元素。我已经复制并粘贴了事件监听器将执行的相同代码，而是在启动时直接将其附加到第一个元素。这也有助于保留可折叠性，因为添加了事件侦听器，而与其他代码无关。

希望这会有所帮助！