如何创建多层手风琴菜单？

Question

我正在尝试使用纯JavaScript创建多层或嵌套的手风琴菜单。整个功能正常运行，只需要解决一个问题：当我单击菜单的一个元素时，整个功能都会做出反应。

这不适用于当前项目。在完成基础课程之后，我只是想扩展我的知识。

我知道解决此问题的简便方法是将函数复制三遍，然后专门针对数组中的每个节点（即使是正确的单词？）。但是，我认为那是做事的错误方式。如您所见，我试图为多个变量创建一个循环。我认为这可能是我的问题，因为这似乎是将所有这些联系在一起的东西。

var accordion = document.getElementsByClassName("accordion");
var dropdown = document.getElementsByClassName("dropdown");
var accordionArrow = document.getElementsByClassName("accordionArrow");
var dropdownArrow = document.getElementsByClassName("dropdownArrow");
var content = document.getElementsByClassName("content");

function accordionFunction() {
  for (j = 0, k = 0, l = 0, m = 0; j < dropdown.length, k < accordionArrow.length, l < dropdownArrow.length, m < content.length; j++, k++, l++, m++) {
    if (dropdown[j].style.maxHeight) {
      dropdown[j].style.maxHeight = null;
      accordionArrow[k].style.transform = null;
      content[m].style.maxHeight = null;
      dropdownArrow[l].style.transform = null;
    } else {
      dropdown[j].style.maxHeight = dropdown[j].scrollHeight + "px";
      accordionArrow[k].style.transform = "rotate(-135deg)";
    }
  }
};

for (var i = 0; i < accordion.length; i++) {
  accordion[i].addEventListener("click", accordionFunction);
};

function accordionSubmenu() {
  for (l = 0, m = 0; l < dropdown.length, m < content.length; l++, m++) {
    if (content[m].style.maxHeight) {
      content[m].style.maxHeight = null;
      dropdownArrow[l].style.transform = null;
    } else {
      content[m].style.maxHeight = content[m].scrollHeight + "px";
      dropdownArrow[l].style.transform = "rotate(-135deg)";
    }
  }
};

for (j = 0; j < dropdown.length; j++) {
  dropdown[j].addEventListener("click", accordionSubmenu)
};

body {
  margin: auto;
  width: 600px;
}

div {
  margin: auto;
}

.accordion {
  background-color: lightblue;
  color: white;
  padding: 3%;
  cursor: pointer;
  width: 300px;
  height: 50px;
}

.accordion .accordionArrow {
  border: solid white;
  border-width: 0 3px 3px 0;
  display: inline-block;
  padding: 3px;
  transform: rotate(45deg);
}

.dropdown {
  color: lightblue;
  padding-left: 3%;
  cursor: pointer;
  width: 300px;
  max-height: 0;
  overflow: hidden;
  transition-duration: 0.2s;
}

.dropdown .dropdownArrow {
  border: solid lightblue;
  border-width: 0 3px 3px 0;
  display: inline-block;
  padding: 3px;
  transform: rotate(45deg);
}

.content {
  font-weight: bold;
  transition: all 0.2s ease;
  padding-left: 5%;
  max-height: 0;
  overflow: hidden;
}

<div>
  <h2 class="accordion">Main 1<i class="accordionArrow"></i></h2>
  <h3 class="dropdown">Submenu 1<i class="dropdownArrow"></i></h3>
  <p class="content">Hello there. We are exposed.</p>
</div>
<div>
  <h2 class="accordion">Main 2<i class="accordionArrow"></i></h2>
  <h3 class="dropdown">Submenu 1<i class="dropdownArrow"></i></h3>
  <p class="content">Hello there. We are exposed again!</p>
</div>
<div>
  <h2 class="accordion">Main 3<i class="accordionArrow"></i></h2>
  <h3 class="dropdown">Submenu 1<i class="dropdownArrow"></i></h3>
  <p class="content">Hello there. We are exposed thrice!</p>
</div>

Answer 1

通过巧妙地使用this关键字（触发事件处理程序的元素）和nextElementSibling属性，您可以更优雅地实现这一目标。

我创建了一个使最大高度为0的元素的类。因此，现在我可以通过添加或删除此类来隐藏和显示元素。

在手风琴函数中，我在单击元素之后切换该类的元素，并删除所有其他元素的类。

在手风琴子菜单中，我只是在nextElementSibling上切换班级。

我个人将使用不同的html结构，通过使用更多级别的元素可以更轻松地切换类，因此您只需要1个函数即可获得x个子菜单。也许对您来说是一个不错的新挑战。

document.querySelectorAll('.accordion').forEach((accordion) => accordion.addEventListener('click', function() {
  //Get All possible hidden elements and loop over it.
  document.querySelectorAll('.dropdown, .content').forEach((collapsible) => {
    //If current element is the same is the next sibling element of the event target toggle the class. Otherwise add it.
    if(collapsible === this.nextElementSibling) {
      collapsible.classList.toggle('maxHeightZero');
    }
    else {
      collapsible.classList.add('maxHeightZero');
    }
  });
}));

document.querySelectorAll('.dropdown').forEach((dropdown) => dropdown.addEventListener('click', function() {
  //toggle the nextElementSibling
  this.nextElementSibling.classList.toggle('maxHeightZero');
}));

body {
  margin: auto;
  width: 600px;
}

div {
  margin: auto;
}

.accordion {
  background-color: lightblue;
  color: white;
  padding: 3%;
  cursor: pointer;
  width: 300px;
  height: 50px;
}

.accordion .accordionArrow {
  border: solid white;
  border-width: 0 3px 3px 0;
  display: inline-block;
  padding: 3px;
  transform: rotate(45deg);
}

.dropdown {
  color: lightblue;
  padding-left: 3%;
  cursor: pointer;
  width: 300px;
  overflow: hidden;
  transition-duration: 0.2s;
}

.dropdown .dropdownArrow {
  border: solid lightblue;
  border-width: 0 3px 3px 0;
  display: inline-block;
  padding: 3px;
  transform: rotate(45deg);
}

.content {
  font-weight: bold;
  transition: all 0.2s ease;
  padding-left: 5%;
  overflow: hidden;
}

.maxHeightZero { 
  max-height: 0;
}

<div>
  <h2 class="accordion">Main 1<i class="accordionArrow"></i></h2>
  <h3 class="dropdown maxHeightZero">Submenu 1<i class="dropdownArrow"></i></h3>
  <p class="content maxHeightZero">Hello there. We are exposed.</p>
</div>
<div>
  <h2 class="accordion">Main 2<i class="accordionArrow"></i></h2>
  <h3 class="dropdown maxHeightZero">Submenu 1<i class="dropdownArrow"></i></h3>
  <p class="content maxHeightZero">Hello there. We are exposed again!</p>
</div>
<div>
  <h2 class="accordion">Main 3<i class="accordionArrow"></i></h2>
  <h3 class="dropdown maxHeightZero">Submenu 1<i class="dropdownArrow"></i></h3>
  <p class="content maxHeightZero">Hello there. We are exposed thrice!</p>
</div>