Question

我为W3Schools示例中的FAQ页面创建了修改后的手风琴。我是Java语言的新手，我需要一些帮助。我想建立一个在展开所有面板和关闭所有面板之间切换的按钮。我可以从另一个人写的创建“关闭所有面板”按钮的博客文章中获得一些帮助，但是现在我想构建一个函数，该功能可以在“全部关闭”和“全部打开”之间切换。我还希望将所有这些都内联，以便可以将这一页代码嵌入另一页。我已经附加了到目前为止创建的代码。

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
<style>
.accordion {
    background-color: none;
    cursor: pointer;
    padding: 30px;
    width: 100%;
    border: #DADCE0;
    border-style: solid;
    border-width: 1px 0px 0px 0px;
    text-align: left;
    outline: none;
    font-family: Google Sans, sans-serif;
    font-weight: medium;
    font-size: 18px;
    line-height: 30px;
    transition: 0.4s;
    color: #1A73E8;
}

.accordion:hover {
    color: #174EA6;
}

.active {
    color: #174EA6;
    border-top-color: #DADCE0;
    border-bottom-color: #174EA6;
    border-style: solid;
    border-width: 1px 0px 2px 0px;
}

.accordion:after {
    font-family: 'Material Icons';
    content: "keyboard_arrow_down"; /*Google keyboard arrow down*/
    font-weight: bold;
    font-size: 24px;
    float: right;
    margin-left: 5px;
}

.active:after {
  font-family: 'Material Icons';
  content: "keyboard_arrow_up"; /*Google keyboard arrow up*/
  font-weight: bold;
  font-size: 24px;
  float: right;
  margin-left: 5px;
}

.panel {
    padding: 0px 18px;
    background-color: white;
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s ease-out;
}

.closeall {
    float: right;
    margin: 1% 2% 0 0;
    cursor: pointer;
}

body {
    font-family: Roboto Light, sans-serif;
    line-height: 26px;
    font-size: 16px;
    color: #202124;
}

a {
    color: #4285f4;
}

</style>
</head>
<body>

<button  class="closeall" onclick="collapseall()">Close all</button>

<button class="accordion">Can I host my own events?</button>
<div class="panel">
  <p>Of course you can!</p>
</div>

<button class="accordion">Are the events for students?</button>
<div class="panel">
  <p>Yes, please see here.</p>
</div>

<button class="accordion">Are the events for teachers?</button>
<div class="panel">
  <p>Yes, please see here.</p>
</div>

<button class="accordion">Are the events for teachers 2?</button>
<div class="panel">
  <p>Yes, please see here 2.</p>
</div>

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

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

function collapseall() {  //problematic part
    var x = document.getElementsByClassName("panel");
    var b;
    for (b = 0; b < x.length; b++) {
        x[b].style.maxHeight = null;
        x[b].previousElementSibling.classList.remove('active');
  }
}
</script>

</body>
</html>

Answer 1

function collapseall() {
    var x = document.getElementsByClassName("accordion");
    var y = 0;
    var b;

    for (b = 0; b < x.length; b++) {
       if(x[b].classList.contains('active'))y++;
    }

    if(x.length==y||y==0){
      for (b = 0; b < x.length; b++) {
         x[b].dispatchEvent(new Event('click'));
      }
    }else{
      for (b = 0; b < x.length; b++) {
         if(x[b].classList.contains('active'))
            x[b].dispatchEvent(new Event('click'));
      }
    }
}

Answer 2

好消息是，您which I implemented here非常适合您。实现该目标的简短方法可能看起来像

// Single reference to all panels 
// Getting them each time is heavy for the browser
var x = document.getElementsByClassName("panel");

// Indicator if we should open or close all panels
var isToggledOff = true;

然后，您需要两个非常相似的功能来打开或折叠所有面板

function collapseAll() { 
    for (var b = 0; b < x.length; b++) {
        x[b].style.maxHeight = null;
        x[b].previousElementSibling.classList.remove('active');
  }
}

function expandAll() {
    for (var b = 0; b < x.length; b++) {
        x[b].style.maxHeight = "58px";
        x[b].previousElementSibling.classList.add('active');
   }
}

最后但并非最不重要的一点是，您需要逻辑来决定我们是否要打开或关闭所有面板以及将来如何处理

function toggle() {
   if (isToggledOff) this.expandAll();
   else this.collapseAll();
   isToggledOff = !isToggledOff
}

您可能要考虑的其他事项

为什么需要设置该maxHeight？将其添加到活动CSS类会更容易吗？
JS中的函数式编程为您提供了超强的功能，为什么不使用.forEach（）方法代替for循环？这可能很棘手，但值得一课：）
您为什么需要previousElementSibling属性？
下次添加问题时，请尝试向人们提供最少的帮助，以使他们可以更轻松地理解问题所在。在这种情况下，您可以从示例中剥离CSS代码：）

替代方式

var x = Array.from(document.getElementsByClassName("panel"));
var isToggledOff = true;
function toggle() {
    x.forEach(el => el
        .previousElementSibling
        .classList
        [isToggledOff ? "add" : "remove"]('active')
    )
   isToggledOff = !isToggledOff
}

创建一个用于扩展和折叠手风琴的切换按钮

2 个答案: