Detailed explanation of CSS: active selector

A paragraph from Active

active is interpreted in English as "active", which means clicking on the mouse. The most common examples of the active selector are probably applied to links. However, opening a link is a momentary action, which does not reflect the characteristics of the active selector well.

Features of Active

In fact, when we open a link with active, there is a process to activate active, which is to click on the module until you release the module. If we do not specify the time this process takes, I think it takes a few tenths of a second by default.

<span style="font-size: 14px"><span style="color: #0000ff"><!</span><span style="color: #ff00ff">DOCTYPE html</span><span style="color: #0000ff">></span>
<span style="color: #0000ff"><</span><span style="color: #800000">html</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"><</span><span style="color: #800000">head</span><span style="color: #0000ff">></span>
    <span style="color: #0000ff"><</span><span style="color: #800000">title</span><span style="color: #0000ff">></span>a<span style="color: #0000ff"></</span><span style="color: #800000">title</span><span style="color: #0000ff">></span>
    <span style="color: #0000ff"><</span><span style="color: #800000">meta </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="content-type"</span><span style="color: #ff0000"> content</span><span style="color: #0000ff">="text/html; charset=UTF-8"</span><span style="color: #0000ff">></span>
      <span style="color: #0000ff"><</span><span style="color: #800000">style</span><span style="color: #0000ff">></span><span style="color: #800000; background-color: #f5f5f5">
      a</span><span style="color: #000000; background-color: #f5f5f5">{</span><span style="color: #ff0000; background-color: #f5f5f5">
        display</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">block</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        width</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">30px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        margin</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">20px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        border-radius</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">8px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        padding</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">20px 50px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        text-align</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">center</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        background</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">green</span><span style="color: #000000; background-color: #f5f5f5">;</span>
      <span style="color: #000000; background-color: #f5f5f5">}</span><span style="color: #800000; background-color: #f5f5f5">
      a:active</span><span style="color: #000000; background-color: #f5f5f5">{</span><span style="color: #ff0000; background-color: #f5f5f5">
        background</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">indigo</span><span style="color: #000000; background-color: #f5f5f5">;</span>
      <span style="color: #000000; background-color: #f5f5f5">}</span>
    <span style="color: #0000ff"></</span><span style="color: #800000">style</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"></</span><span style="color: #800000">head</span><span style="color: #0000ff">></span>
  
  <span style="color: #0000ff"><</span><span style="color: #800000">body</span><span style="color: #0000ff">></span>
    <span style="color: #0000ff"><</span><span style="color: #800000">a </span><span style="color: #ff0000">href</span><span style="color: #0000ff">="paris.jpg"</span><span style="color: #0000ff">></span>link<span style="color: #0000ff"></</span><span style="color: #800000">a</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"></</span><span style="color: #800000">body</span><span style="color: #0000ff">></span>
<span style="color: #0000ff"></</span><span style="color: #800000">html</span><span style="color: #0000ff">></span></span>

We can adjust this time through the transition attribute.

<span style="color: #000000; font-size: 14px">      a:active{
        background:indigo;
        transition:3s;
      }</span>

Readers can do an experiment, change the value of transition, and then test the time spent by the avtive selector.

ACTIVE Example

<span style="font-size: 14px"><span style="color: #0000ff"><!</span><span style="color: #ff00ff">DOCTYPE html</span><span style="color: #0000ff">></span>
<span style="color: #0000ff"><</span><span style="color: #800000">html</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"><</span><span style="color: #800000">head</span><span style="color: #0000ff">></span>
    <span style="color: #0000ff"><</span><span style="color: #800000">title</span><span style="color: #0000ff">></span>a<span style="color: #0000ff"></</span><span style="color: #800000">title</span><span style="color: #0000ff">></span>
    <span style="color: #0000ff"><</span><span style="color: #800000">meta </span><span style="color: #ff0000">name</span><span style="color: #0000ff">="content-type"</span><span style="color: #ff0000"> content</span><span style="color: #0000ff">="text/html; charset=UTF-8"</span><span style="color: #0000ff">></span>
    <span style="color: #0000ff"><</span><span style="color: #800000">style</span><span style="color: #0000ff">></span><span style="color: #800000; background-color: #f5f5f5"> 
       div
      </span><span style="color: #000000; background-color: #f5f5f5">{</span><span style="color: #ff0000; background-color: #f5f5f5">
        width</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">100px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        height</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">100px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        background</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">red</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        transition</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5"> 5s</span><span style="color: #000000; background-color: #f5f5f5">;</span>
       <span style="color: #000000; background-color: #f5f5f5">}</span><span style="color: #800000; background-color: #f5f5f5">

        div:active
       </span><span style="color: #000000; background-color: #f5f5f5">{</span><span style="color: #ff0000; background-color: #f5f5f5">
        width</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">300px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        height</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">300px</span><span style="color: #000000; background-color: #f5f5f5">;</span><span style="color: #ff0000; background-color: #f5f5f5">
        transition</span><span style="color: #000000; background-color: #f5f5f5">:</span><span style="color: #0000ff; background-color: #f5f5f5">3s</span><span style="color: #000000; background-color: #f5f5f5">;</span>
        <span style="color: #000000; background-color: #f5f5f5">}</span>
      <span style="color: #0000ff"></</span><span style="color: #800000">style</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"></</span><span style="color: #800000">head</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"><</span><span style="color: #800000">body</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"><</span><span style="color: #800000">div</span><span style="color: #0000ff">></</span><span style="color: #800000">div</span><span style="color: #0000ff">></span>
  <span style="color: #0000ff"></</span><span style="color: #800000">body</span><span style="color: #0000ff">></span>
<span style="color: #0000ff"></</span><span style="color: #800000">html</span><span style="color: #0000ff">></span>
             </span>

There are two transitions here, which means there are two transitions.

1. 1. The first transition is to activate the active selector. At this time, the transition in div:avtive works.
   2. The second transition is when the mouse is released and the size of the image returns to normal. At this time, the transition in the div takes effect.

If the reader only sets the transition in the div, then the transition time of the selector will default to the transition in the div.

If readers are interested, they can also try the combination of transition and other selectors.