What is :hover::after?-CodePudding

I was following a youtube tutorial, in which a CSS hover effect was used so that when you bring you cursor on the navbar items, a line emerged gradually from the center. How does the whole :hover::after thing work?

This is the CSS code they showed in the video :

  nav{
  display: flex;
  padding: 2% 6%;
  justify-content: space-between;
  align-items: center;
  position: sticky;
}

nav img{
  width: 150px;
}

.nav-links{
  flex: 1;
  text-align: right;
  gap: 2rem;
}

.nav-links ul li{
  list-style: none;
  display: inline-block;
  padding: 8px 12px;
  position: relative;
}

.nav-links ul li a{
  color: #ffffff;
  font-size: 13px;
  text-decoration: none;
}

.nav-links ul li a::after{
  content: '';
  width: 0%;
  height: 2px;
  background: #f44336;
  display: block;
  margin: auto;
  transition: 0.5s;
}

.nav-links ul li a:hover::after{
  width: 100%;
}```

CodePudding user response：

When hovering on the element in your case <a> tag, you apply a style on the ::after pseudo-element. In the example code I see that you give the pseudo-element a with of 100% and that way you change the initial value of the width witch is 0.

CodePudding user response：

::after and :hover are pseudo-elements. If you have a:hover, the following styles will apply on the element when hovering over it. But, when you have a:hover::after, the following styles will apply on the pseudo-element ::after, when hovering over the element. It this case, the ::after pseudo-element represents the expanding line. And by the way to make it clear what is ::after, in CSS using the content attribute, you can also define the HTML content to be shown in the ::after pseudo-element, but in this case, you don't need to put any content there, it's just an empty shape.