How to Apply .nextElementSibling to the next item of a dropdown menu

Question

I have a menu that contains sub-items, when I click on them it pops up showing the items. I managed to open the first item, but I can't do the same with the second. I'm trying to use .nextElementSibling for this, but I can't. What am I doing wrong ?

var dropdownBtn = document.querySelector('.menu-btn');

dropdownBtn.addEventListener('click',()=>{
var menuContent = document.querySelector('.drop_container');
    menuContent.classList.toggle("show");
  
})

.menu-btn {
  background: #e0e0e0;
  padding: 10px;
  margin: 5px 0px 0px 0px;
}

.menu-btn:hover {
  background: #000;
  color: #fff;
}


.drop_container {
   display: none;
   background-color: #017575;
   transition: 0.3s;
   opacity: 0;
}

.drop_container.show {
  display: contents;
  visibility: visible;
  opacity: 1;
}

.drop_container > .item {
  display: flex;
  flex-direction: column;
  margin-left: 10px;
  padding: 10px 0px 0px 0px;
}

<div class="dropdown-menu">

<div class="menu-btn">One</div>
<div class="drop_container">
  <a class="item" href="#">Contact Us</a>
  <a class="item" href="#">Visit Us</a>
</div>

<div class="menu-btn">Two</div>
<div class="drop_container">
  <a class="item" href="#">Contact Us</a>
  <a class="item" href="#">Visit Us</a>
</div> 

</div>

Answer 1

1. Collect each .menu-btn in a NodeList, then run that through with .forEach().
2. On each iteration reference the menuContent as this.nextElementSibling.
3. this is the .menu-btn that user clicked, in order to use this do not use an arrow function. If you prefer an arrow function, use the equivalent (in this situation) e.target in place of this.

const dropdownBtn = document.querySelectorAll('.menu-btn');

dropdownBtn.forEach(btn => btn.addEventListener('click', function() {
  const menuContent = this.nextElementSibling;
  menuContent.classList.toggle("show");
}));

.menu-btn {
  background: #e0e0e0;
  padding: 10px;
  margin: 5px 0px 0px 0px;
}

.menu-btn:hover {
  background: #000;
  color: #fff;
}

.drop_container {
  display: none;
  background-color: #017575;
  transition: 0.3s;
  opacity: 0;
}

.drop_container.show {
  display: contents;
  visibility: visible;
  opacity: 1;
}

.drop_container>.item {
  display: flex;
  flex-direction: column;
  margin-left: 10px;
  padding: 10px 0px 0px 0px;
}

<div class="dropdown-menu">

  <div class="menu-btn">One</div>
  <div class="drop_container">
    <a class="item" href="#">Contact Us</a>
    <a class="item" href="#">Visit Us</a>
  </div>

  <div class="menu-btn">Two</div>
  <div class="drop_container">
    <a class="item" href="#">Contact Us</a>
    <a class="item" href="#">Visit Us</a>
  </div>

</div>