
:nth-child()
comes in really handy. These selectors let you apply styles based on the position of an element among its siblings, which is super useful for things like zebra-striping tables, styling every other item in a list, or making layout adjustments without touching your HTML.

How :nth-child()
Actually Works
<p> At first glance, :nth-child()
might seem a bit confusing — especially with that odd-looking formula an b
. But once you get the hang of it, it's pretty straightforward.

-
<li> The basic idea is that
:nth-child(n)
selects the nth child of its parent.
<li> You can use formulas like 2n 1
or keywords like odd
and even
.

li:nth-child(2n) { background-color: #f0f0f0; }<p> This would select every even-numbered
<li>
in a list and give it a light gray background — perfect for altering row colors in a table or list layout.<p> One common mistake is thinking :nth-child()
looks only at elements of the same type. It actually counts all children, regardless of tag type. So if you have a mix of <p>
, <div>
, and <span>
inside a container, :nth-child()
will count them all.Other Useful Structural Pseudo-Classes
<p> While:nth-child()
is powerful, there are several related pseudo-classes that are worth knowing:- <li>
:first-child
– targets the first child if it matches the element type.<li> :last-child
– same logic, but for the last child.<li> :nth-of-type()
– similar to :nth-child()
, but only considers elements of the matching type.<li> :only-child
– apply if the element is the only one inside its parent.<div> <p>First paragraph</p> <span>Just a span</span> <p>Second paragraph</p> </div><p> Then:
p:nth-child(1) { color: red; } /* Won't match anything because first child is a <p>, but it's not ap:nth-child(1) */ p:nth-of-type(1) { color: blue; } /* This matches the first <p> */ p:nth-of-type(2) { color: green; } /* Matches the second <p> */<p> So when working with mixed content,
:nth-of-type()
is usually more reliable for targeting specific element types.Practical Uses in Layouts and Lists
<p> These selectors are especially handy in real-world layouts where you want to tweak spacing or visual hierarchy without bloating your HTML with extra classes.<p> Some examples:- <li><p> Remove margin from the last item in a grid or flexbox layout:
.card:last-child { margin-right: 0; }<li><p> Style the first paragraph differently (like making it larger):
p:first-of-type { font-size: 1.2em; font-weight: bold; }<li><p> Highlight the first and last columns in a table:
td:first-child { border-left: 1px solid #ccc; } td:last-child { border-right: 1px solid #ccc; }<p> They're also great for responsive design tweaks — say you want to hide certain items on small screens based on their position, or adjust padding on mobile only for specific children.
A Few Gotchas to Keep in Mind
<p> Like any CSS feature, these selectors can trip you up if you're not careful. <p> Here are a few things to watch out for:-
<li> Whitespace matters — sometimes an invisible text node (like a line break) can throw off your count.
<li> Performance isn't usually an issue , but avoid overusing complex
:nth-child()
patterns on large pages.
<li> Test visually — browser dev tools sometimes make it hard to see what's being selected, so double-check how your styles are applied.
<p> That's basically it. Once you get used to using structural pseudo-classes, they become second nature — and they save you from writing extra markup or JavaScript just to handle simple styling logic.
The above is the detailed content of Using CSS nth-child and other structural pseudo-classes. For more information, please follow other related articles on the PHP Chinese website!

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