Show flyout menu using mouseover event

Question

I have a popup menu and I'm trying to use mouseover events to toggle it, but it doesn't seem to be working as expected. I tried using CSS hover events by positioning the div like this: .hero-list-block a:hover .flyout-menu

But this is of no use. Any suggestions on how to fix this/improve this? Thanks

const flyoutLink = document.querySelector('.flyout-link');
const flyoutMenu = document.querySelector('.flyout-menu');

flyoutLink.addEventListener('mouseover', () => {
  flyoutMenu.classList.toggle('.flyout-menu-show');
})

.grid-hero-wrapper {
  grid-template-columns: 100px 1fr;
  gap: 15px;
  margin-top: 15px;
  display: grid;
}

.hero-categories-block {
  background: #fff;
  border: 1px solid #28282b;
}

.hero-categories-list {
  display: flex;
  flex-direction: column;
  padding: 5px 0;
  height: 100%;
}

.flyout-menu-show {
  opacity: 1;
  visibility: visible;
}

.flyout-menu {
  background: #fff;
  border: 1px solid #28282b;
  position: absolute;
  top: 0;
  width: 100%;
  height: 100%;
  opacity: 0;
  visibility: hidden;
  position: absolute;
  z-index: 999;
}

.hero-categories-list a {
  display: flex;
  align-items: center;
  flex-grow: 1;
  font-size: 0.75rem;
  height: 22px;
  color: #333;
}

.hero-slider-block {
  position: relative;
}

<link href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" rel="stylesheet" />
<div class="grid-hero-wrapper">
  <div class="hero-categories-block">
    <div class="hero-categories-list">
      <a href="#" class="flyout-link">Flyout</a>
      <a href="#" class="flyout-link">Flyout</a>
    </div>
  </div>
  <div class="hero-slider-block">
    <div id="carouselExampleSlidesOnly" class="carousel slide" data-bs-ride="carousel">
      <div class="carousel-inner">
        <div class="carousel-item active hero-slider-img">
          <img src="https://images.unsplash.com/photo-1507525428034-b723cf961d3e?ixlib=rb-4.0.3&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=1173&q=80" class="d-block w-100">
        </div>
      </div>
    </div>
    <div class="flyout-menu">
      <h1>This is my flyout menu</h1>
    </div>
  </div>
</div>

Answer 1

Due to the peculiarities of css selectors, this does not work.

The

.flyout-menu-show selector is declared before the .flyout-menu selector, and they have the same specificity. Therefore, only the latest ones apply to your elements.

Change

.flyout-menu-show {
  opacity: 1;
  visibility: visible;
}

to

.flyout-menu.flyout-menu-show {
  opacity: 1;
  visibility: visible;
}

This will create a selector with higher specificity and it will be applied correctly :). Working codepen for the example: https://codepen.io/aSH-uncover/pen/PoaboWo

It might also be worth reading this page: https://developer.mozilla.org/en-US/docs/Web/CSS/Specificity