We've seen how there are mainly 3 types of CSS selectors.
Right?
In this post we all will explore CSS Pusedo class in a very easy way.
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-
generic where
p
in CSS targets<p>
HTML elements -
classes where
.intro
in CSS targets HTML elements with aclass="intro"
attribute -
ids where
#logo
in CSS targets HTML elements with aid="logo"
attribute
All of these selectors can have pseudo-classes attached to them. A pseudo-class:
- defines a particular state of the element
- is a keyword that starts with a colon
:
Syntax
A pseudo-class can't exist on its own. It must be attached to a selector. The pseudo-class will only define a particular state of that selector.
The syntax looks like this:
.selector:pseudo-class{ }
There is no space between the selector and the pseudo-class, to signify that they are linked together.
:hover
For example, a common pseudo-class used is :hover
, which will apply a CSS style when the targeted element is hovered. Let's test it on links.
a{ color: blue;}
a:hover{ color: red;}
<div class="result" id="result-821">
<p>Hover <a>this link</a> and see how it turns red.</p>
</div>
The first line defines how all <a>
HTML elements should look like (blue).
The second line defines how <a>
should look like when hovered (red).
The second line targets the same HTML elements but only when something specific happens (in this case, being hovered).
:visited
This pseudo-class targets links that have been visited. By default, links are blue and turn purple when you've visited them. Google results work like that.
a{ color: dodgerblue;}
a:visited{ color: rebeccapurple;}
<a href="https://www.google.com">Google</a>
<a href="https://twitter.com">Twitter</a>
<a href="https://www.facebook.com">Facebook</a>
<a href="https://www.mozilla.org">Mozilla</a>
<a href="https://marksheet.io/visited.html">MarkSheet</a>
<div class="result" id="result-8211">
<a href="https://www.google.com">Google</a>
<a href="https://twitter.com">Twitter</a>
<a href="https://www.facebook.com">Facebook</a>
<a href="https://www.mozilla.org">Mozilla</a>
<a href="/html/visited.html">MarkSheet</a>
</div>
Applying a different for visited links is often overlooked but comes in handy for users browsing a list of results. It easily helps them visualize where they have already been.
:focus
This pseudo-class happens when an HTML element is in focus. This is particularly useful for HTML inputs.
.form-input{ border: 2px solid grey; padding: 5px;}
.form-input:focus{ background: lightyellow; border-color: blue; outline: none;}
<div class="result" id="result-822">
<input class="form-input" placeholder="First name">
</div>
The outline: none;
rule removes the glow from the input.
:first-child and :last-child
These pseudo-classes are related to the HTML hierarchy. They target HTML elements depending on the order in which they appear in the code.
<ul>
<li>One</li>
<li>Two</li>
<li>Three</li>
<li>Four</li>
</ul>
li:first-child{ background: greenyellow;}
li:last-child{ background: lightsalmon;}
<div class="result" id="result-823">
<ul>
<li>One</li>
<li>Two</li>
<li>Three</li>
<li>Four</li>
</ul>
</div>
As you can see, no CSS class is applied to the first and last <li>
. Their position in the hierachy defines whether the CSS rule is applied.
If we were to add a 5th list item, and using the same CSS, the styling would automatically change:
<div class="result" id="result-824">
<ul>
<li>One</li>
<li>Two</li>
<li>Three</li>
<li>Four</li>
<li>Five</li>
</ul>
</div>
:nth-child
This pseudo-class is a more global version of :first-child
and :last-child
. With :nth-child
, you can calculate which child element you want to target.
For example, if you want to target the second child, you would use :nth-child(2)
:
li:nth-child(2){ background: violet;}
<div class="result" id="result-825">
<ul>
<li>One</li>
<li>Two</li>
<li>Three</li>
<li>Four</li>
</ul>
</div>
odd and even
While using a number is straightforward, the :nth-child
comes with 2 keywords:
-
:nth-child(odd)
will target every odd element -
:nth-child(even)
will target every even element
li:nth-child(odd){ background: gold;}
<div class="result" id="result-826">
<ul>
<li>One</li>
<li>Two</li>
<li>Three</li>
<li>Four</li>
</ul>
</div>
The n iterator
The most powerful aspect of :nth-child
is how it can target elements based upon calculations by using the n
keyword.
The n
value increments from zero 0
to the number of child elements present.
What if you want to target every third element?
li:nth-child(3n){ background: hotpink;}
<div class="result" id="result-827">
<ul>
<li>One</li>
<li>Two</li>
<li>Three</li>
<li>Four</li>
<li>Five</li>
<li>Six</li>
<li>Seven</li>
</ul>
</div>
In our case, n
starts at zero and ends at six.
Computers start counting at zero. And because there are seven elements in our list, we will go up until six, because 0-1-2-3-4-5-6 represents seven items.
You can read :nth-child(3n)
as "Target each element whose position is dividable by 3". In our case, it targeted both the 3rd and 6th list items:
-
3 times 0
is zero -
3 times 1
is the 3rd element -
3 times 2
is the 6th element
n + 1
What if you want to target the 1st item and every third item after that?
li:nth-child(3n+1){ background: limegreen;}
Here is the html code:
<div class="result" id="result-828">
<ul>
<li>One</li>
<li>Two</li>
<li>Three</li>
<li>Four</li>
<li>Five</li>
<li>Six</li>
<li>Seven</li>
</ul>
</div>
The
3n+1
has two parts:
-
3n
selects every 3rd item -
+1
offsets the start by 1
This is how the calculations were processed:
-
3 times 0 plus 1
is 1 -
3 times 1 plus 1
is 4 -
3 times 2 plus 1
is 7
The n
iterator is very versatile. It's hard to find the right calculation, so just test it out to find the right selection.
Other pseudo-classes
There are dozens of pseudo-classes available, some of them for very specific states. The most used ones are the ones we've covered.
<style type="text/css">
#result-821 a{ color: blue;}
#result-821 a:hover{ color: red;}
#result-8211 a{ color: dodgerblue;}
#result-8211 a:visited{ color: rebeccapurple;}
#result-822{ padding: 1rem;}
#result-822 input{ border: 2px solid lightgrey; padding: 5px;}
#result-822 input:focus{ background: lightyellow; border-color: blue; outline: none;}
#result-823 li:first-child{ background: greenyellow;}
#result-823 li:last-child{ background: lightsalmon;}
#result-824 li:first-child{ background: greenyellow;}
#result-824 li:last-child{ background: lightsalmon;}
#result-825 li:nth-child(2){ background: violet;}
#result-826 li:nth-child(odd){ background: gold;}
#result-827 li:nth-child(3n){ background: hotpink;}
#result-828 li:nth-child(3n+1){ background: limegreen;}
</style>
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