search
HomeWeb Front-endCSS TutorialSome techniques for using pseudo-classes, pseudo-elements and adjacent element selectors in CSS

A few days ago, I encountered a page requirement like this:

Some techniques for using pseudo-classes, pseudo-elements and adjacent element selectors in CSS

A comment box. The button behind it has two states: like or send comment. The send button is divided into clickable and comment based on whether there are words in the input box. Both states are unclickable.

Requirements:
No text, no focus - like
No text, focus - send in gray
With text - send in red

If implemented with JS, you need to monitor the change and focus events of the input box, which is more troublesome. But similar effects can be achieved using pseudo-classes in CSS.

<input type="text" class="input" required>
<div class="like">点赞</div>
<div class="send">发送</div>
.send {
  display: none;
}

.input:focus ~ .send {
  display: block;
}

.input:valid ~ .send {
  display: block;
  color: red;
}


.input:focus ~ .like, .input:valid ~ .like {
  display: none;
}

(If the comment box is implemented with a div element with the contenteditable attribute, you can use the :empty pseudo-class instead of :valid.)

So there are many pseudo-classes and pseudo-elements in CSS3, and some of them, if used cleverly, can achieve a lot Effects that originally required JS to be achieved.

Placeholder of div with contenteditable attribute

For some reasons, we sometimes use div with contenteditable attribute instead of input or textarea as input box. For example, divs can automatically adjust their height based on their content. But the div element does not support the placeholder attribute. How to display a default text when the div content is empty? You can use the :empty pseudo-class.

  <div class="input" contenteditable placeholder="请输入文字"></div>
rrree

Draw a grid

This is what I saw on Meituan’s mobile page:

Some techniques for using pseudo-classes, pseudo-elements and adjacent element selectors in CSS

We need to draw a grid in this area of ​​the city list. Of course, our first thought is to use the border attribute, but the designer has a requirement that if there is only one or two cities in the last row, there must be a blank grid behind it for the sake of beauty. Like this:

Some techniques for using pseudo-classes, pseudo-elements and adjacent element selectors in CSS

How to draw the vertical lines of the grid on Meituan’s page? It is drawn using ::after and ::before elements.

.input:empty::before {
  content: attr(placeholder);
}

Created two pseudo-elements with a height of 100%, using their borders as vertical lines of the table. This solution can meet the designer's requirements without adding blank page elements and destroying semantics. But the limitation is that only four vertical lines can be drawn at most, which means that the table can have up to 5 columns.

Tab switching

It is also possible to implement tab switching using pure CSS. It mainly uses the :checked pseudo-class and adjacent selector of the radio button element. Because it is a radio button, it is guaranteed that only one tab is active at the same time. If you do not require more complex effects, the tab switching effect achieved by pure CSS is much simpler and more reliable than JS.

.table:before {
  content: &#39;&#39;;
  position: absolute;
  width: 25%;
  left: 25%;
  height: 100%;
  border-left: 1px solid #ddd8ce;
  border-right: 1px solid #ddd8ce;
}

.table:after {
  content: &#39;&#39;;
  position: absolute;
  width: 10%;
  left: 75%;
  height: 100%;
  border-left: 1px solid #ddd8ce;
  border-right: none;
}
  <input id="tab1" type="radio" name="tabs" checked>
  <label for="tab1">TAB1</label>
  <input id="tab2" type="radio" name="tabs">
  <label for="tab2">TAB2</label>

  <div id="content1" class="tab-content">CONTENT1<div>  
  <div id="content2" class="tab-content">CONTENT2</div>

In addition, using pseudo-classes of form elements, label elements can be used to replace form elements such as radio buttons and check boxes themselves, because it is very difficult to define styles for the form elements themselves.

Perception of the number of child elements

This is one of the most complex techniques I have ever seen. It comes from this article. It does not rely on JS to apply different styles according to the number of child elements.

For example, this CSS:

  input, .tab-content{
    display: none;
  }
  #tab1:checked ~ #content1,
  #tab2:checked ~ #content2 {
    display: block;
  }

can achieve this effect: if the number of li elements in the .list is greater than or equal to 4, it will be displayed in red.

How is this achieved?

:nth-last-child(n+4) This selector means the fourth to last and previous elements, with ~ li added after it, which means the li element after the element that meets the previous conditions.

If the total number of elements is less than 4, there will be no elements that match:nth-last-child(n+4) (there are not four in total, so there is no fourth-to-last element), then li:nth-last-child( n+4) ~ li will not select any elements.

But if you only use ~ li, the first li will not be matched, so li:nth-last-child(n+4):first-child is added.

This also enables the application of different styles based on the number of elements.


Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Draggin' and Droppin' in ReactDraggin' and Droppin' in ReactApr 17, 2025 am 11:52 AM

The React ecosystem offers us a lot of libraries that all are focused on the interaction of drag and drop. We have react-dnd, react-beautiful-dnd,

Fast SoftwareFast SoftwareApr 17, 2025 am 11:49 AM

There have been some wonderfully interconnected things about fast software lately.

Nested Gradients with background-clipNested Gradients with background-clipApr 17, 2025 am 11:47 AM

I can't say I use background-clip all that often. I'd wager it's hardly ever used in day-to-day CSS work. But I was reminded of it in a post by Stefan Judis,

Using requestAnimationFrame with React HooksUsing requestAnimationFrame with React HooksApr 17, 2025 am 11:46 AM

Animating with requestAnimationFrame should be easy, but if you haven’t read React’s documentation thoroughly then you will probably run into a few things

Need to scroll to the top of the page?Need to scroll to the top of the page?Apr 17, 2025 am 11:45 AM

Perhaps the easiest way to offer that to the user is a link that targets an ID on the element. So like...

The Best (GraphQL) API is One You WriteThe Best (GraphQL) API is One You WriteApr 17, 2025 am 11:36 AM

Listen, I am no GraphQL expert but I do enjoy working with it. The way it exposes data to me as a front-end developer is pretty cool. It's like a menu of

Weekly Platform News: Text Spacing Bookmarklet, Top-Level Await, New AMP Loading IndicatorWeekly Platform News: Text Spacing Bookmarklet, Top-Level Await, New AMP Loading IndicatorApr 17, 2025 am 11:26 AM

In this week's roundup, a handy bookmarklet for inspecting typography, using await to tinker with how JavaScript modules import one another, plus Facebook's

Various Methods for Expanding a Box While Preserving the Border RadiusVarious Methods for Expanding a Box While Preserving the Border RadiusApr 17, 2025 am 11:19 AM

I've recently noticed an interesting change on CodePen: on hovering the pens on the homepage, there's a rectangle with rounded corners expanding in the back.

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Best Graphic Settings
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. How to Fix Audio if You Can't Hear Anyone
1 months agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Chat Commands and How to Use Them
1 months agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

EditPlus Chinese cracked version

EditPlus Chinese cracked version

Small size, syntax highlighting, does not support code prompt function

WebStorm Mac version

WebStorm Mac version

Useful JavaScript development tools

Safe Exam Browser

Safe Exam Browser

Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.

SublimeText3 English version

SublimeText3 English version

Recommended: Win version, supports code prompts!

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment