How do I create a multilayer accordion menu?

Question

I am trying to create a multilayer or nested accordion menu using pure JavaScript. The whole thing is functioning correctly expect for one issue: when I click on one element of the menu, the entire thing reacts.

This is not for a current project. I am simply trying to expand my knowledge after taking a basic course.

I know the easy-but-bloated way to fix this would be to replicate the functions three times and then specifically target each node (is that even the right word?) in the array. However, I image that would be the wrong way to do things. As you’ll see, I attempted to create a loop for multiple variables. I think this might be my issue because it seems to be the thing that is linking all of them together.

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

With some smart use of the this keyword (the element that triggered the event handler) and the nextElementSibling property you can achieve this in a more elegant way.

I made a class to make elements max-height 0. So now i can hide and show elements by just adding or removing this class.

In the accordion function I toggle this class for the element after the clicked element and remove the class for all others.

In the accordion submenu I just toggle the class on the nextElementSibling.

Personally I would make a different html structure where you can toggle classes easier by using more levels of elements so you would only need 1 function for x amount of submenu's. Maybe a nice new challenge for you.

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>