偽類和類的特異性權(quán)重相同。在CSS中，偽類（如:hover）與常規(guī)類（如.btn）處?kù)锻惶禺愋詫蛹?jí)，均為第三類選擇器，每項(xiàng)貢獻(xiàn)一個(gè)類級(jí)別的特異性分?jǐn)?shù)。例如，.btn和a:hover的特異性同為0,0,1,0；而ID選擇器（#nav）則增加更高權(quán)重。儘管偽類本身不提升特異性值，但其應(yīng)用狀態(tài)（如懸停或聚焦）可能使其在級(jí)聯(lián)中優(yōu)先生效。實(shí)際使用時(shí)應(yīng)合理搭配偽類與類以控製樣式優(yōu)先級(jí)，並避免過(guò)度依賴偽類進(jìn)行關(guān)鍵UI更改。

When you're styling elements with CSS, choosing between a pseudo-class and a regular class can make a real difference in how your styles behave. So what's the specificity of a pseudo-class compared to a class? The short answer is: a pseudo-class has the same specificity weight as a regular class .

That might be surprising at first, but it's important to understand how this affects your CSS rules when they start overlapping or conflicting.

How Specificity Is Calculated

Specificity in CSS is like a scoring system that browsers use to determine which style rule applies when multiple ones match the same element. It's broken down into four categories:

• Inline styles (like style="color:red" ) – highest score
• IDs ( #header )
• Classes, attributes, and pseudo-classes ( .btn , [type="text"] , :hover )
• Elements and pseudo-elements ( div , ::before )

Each of these contributes a different "weight" to the overall specificity. A pseudo-class falls into the third category — just like a regular class — so each one adds one class-level point to the specificity score.

For example:

• a:hover has a specificity of 0,0,1,0 (one pseudo-class)
• .link also has 0,0,1,0 (one class)
• #nav a:hover becomes 0,1,1,1 (ID class element)

This means if two selectors have the same number of IDs, classes, etc., the one that comes later in the stylesheet wins — regardless of whether it uses a pseudo-class or not.

When Pseudo-Classes Can Feel More Specific

Even though their base specificity value is the same as a class, pseudo-classes can sometimes seem more powerful because of when they apply.

Take :hover , for instance. If you have:

 .btn {
  color: blue;
}

.btn:hover {
  color: red;
}

Both .btn and .btn:hover are class-level specificity. But the hover version will override the normal one because of the cascade — not specificity — since it's a more specific state of the element.

Another common case is form states like :focus or :invalid . These often need to override default styles, and combining them with classes helps ensure the right behavior without resorting to !important .

Practical Tips for Managing Pseudo-Class Specificity

Here are some things to keep in mind when working with pseudo-classes:

• You can't nest pseudo-classes inside other selectors in plain CSS (though preprocessors like Sass let you do it).
• Use them wisely — stacking too many pseudo-classes (eg, a:link:hover:visited ) can get messy and hard to maintain.
• If you're trying to override a style that uses a pseudo-class, match or exceed its specificity. For example, if a library uses .button:hover , don't try to beat it with just .button .
• Don't rely on pseudo-classes alone for critical UI changes — always test how they behave across devices and user interactions.

If you're ever unsure, tools like browser dev tools will show you which styles are being applied and why — helping you debug specificity issues quickly.

So while pseudo-classes aren't technically more specific than regular classes, they play an important role in targeting dynamic states and conditions of elements. Knowing how they stack up helps you write cleaner, more predictable CSS.

基本上就這些。

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