pseudo-elements

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Pseudo Elements

Review CSS and JavaScript for pseudo-element best practices and View Transitions API usage.

审查CSS和JavaScript中pseudo-element的最佳实践及View Transitions API的使用情况。

How It Works

工作原理

Read the specified files (or prompt user for files/pattern)
Check against all rules below
Output findings in
```
file:line
```
format

读取指定文件（或提示用户输入文件/匹配模式）
对照以下所有规则进行检查
以
```
file:line
```
格式输出检查结果

Rule Categories

规则分类

Priority	Category	Prefix
1	Before/After	`pseudo-`
2	View Transitions	`transition-`
3	Native Styling	`native-`

优先级	分类	前缀
1	Before/After	`pseudo-`
2	View Transitions	`transition-`
3	Native Styling	`native-`

Rules

规则

Before/After Rules

Before/After 规则

pseudo-content-required

pseudo-content-required

::before and ::after require content property to render.

Fail:

css

.button::before {
  position: absolute;
  background: var(--gray-3);
}

Pass:

css

.button::before {
  content: "";
  position: absolute;
  background: var(--gray-3);
}

::before和::after伪元素需要content属性才能渲染。

失败示例：

css

.button::before {
  position: absolute;
  background: var(--gray-3);
}

通过示例：

css

.button::before {
  content: "";
  position: absolute;
  background: var(--gray-3);
}

pseudo-over-dom-node

pseudo-over-dom-node

Use pseudo-elements for decorative content instead of extra DOM nodes.

Fail:

tsx

<button className={styles.button}>
  <span className={styles.background} /> {/* Unnecessary DOM node */}
  Click me
</button>

Pass:

tsx

<button className={styles.button}>
  Click me
</button>

css

.button::before {
  content: "";
  /* decorative background */
}

使用伪元素实现装饰性内容，而非额外的DOM节点。

失败示例：

tsx

<button className={styles.button}>
  <span className={styles.background} /> {/* 不必要的DOM节点 */}
  Click me
</button>

通过示例：

tsx

<button className={styles.button}>
  Click me
</button>

css

.button::before {
  content: "";
  /* 装饰性背景 */
}

pseudo-position-relative-parent

pseudo-position-relative-parent

Parent must have position: relative for absolute pseudo-elements.

Fail:

css

.button::before {
  content: "";
  position: absolute;
  inset: 0;
}
/* .button has no position */

Pass:

css

.button {
  position: relative;
}

.button::before {
  content: "";
  position: absolute;
  inset: 0;
}

当伪元素使用absolute定位时，其父元素必须设置position: relative。

失败示例：

css

.button::before {
  content: "";
  position: absolute;
  inset: 0;
}
/* .button未设置position属性 */

通过示例：

css

.button {
  position: relative;
}

.button::before {
  content: "";
  position: absolute;
  inset: 0;
}

pseudo-z-index-layering

pseudo-z-index-layering

Pseudo-elements need z-index to layer correctly with content.

Fail:

css

.button::before {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--gray-3);
}
/* Covers button text */

Pass:

css

.button {
  position: relative;
  z-index: 1;
}

.button::before {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--gray-3);
  z-index: -1;
}

伪元素需要设置z-index以与内容正确分层显示。

失败示例：

css

.button::before {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--gray-3);
}
/* 覆盖了按钮文字 */

通过示例：

css

.button {
  position: relative;
  z-index: 1;
}

.button::before {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--gray-3);
  z-index: -1;
}

pseudo-hit-target-expansion

pseudo-hit-target-expansion

Use negative inset values to expand hit targets without extra markup.

Fail:

tsx

<div className={styles.wrapper}> {/* Extra wrapper for hit target */}
  <a className={styles.link}>Link</a>
</div>

Pass:

css

.link {
  position: relative;
}

.link::before {
  content: "";
  position: absolute;
  inset: -8px -12px;
}

使用负inset值扩展点击目标区域，无需额外标记。

失败示例：

tsx

<div className={styles.wrapper}> {/* 为扩展点击目标添加的额外容器 */}
  <a className={styles.link}>Link</a>
</div>

通过示例：

css

.link {
  position: relative;
}

.link::before {
  content: "";
  position: absolute;
  inset: -8px -12px;
}

View Transitions Rules

View Transitions 规则

transition-name-required

transition-name-required

Elements participating in view transitions need view-transition-name.

Fail:

document.startViewTransition(() => {
  // No view-transition-name assigned
  targetImg.src = newSrc;
});

Pass:

sourceImg.style.viewTransitionName = "card";
document.startViewTransition(() => {
  sourceImg.style.viewTransitionName = "";
  targetImg.style.viewTransitionName = "card";
});

参与视图过渡的元素需要设置view-transition-name属性。

失败示例：

document.startViewTransition(() => {
  // 未设置view-transition-name
  targetImg.src = newSrc;
});

通过示例：

sourceImg.style.viewTransitionName = "card";
document.startViewTransition(() => {
  sourceImg.style.viewTransitionName = "";
  targetImg.style.viewTransitionName = "card";
});

transition-name-unique

transition-name-unique

Each view-transition-name must be unique on the page during transition.

Fail:

css

.card {
  view-transition-name: card;
}
/* Multiple cards with same name */

Pass:

// Assign unique name only to transitioning element
element.style.viewTransitionName = `card-${id}`;

过渡期间，页面上每个view-transition-name必须唯一。

失败示例：

css

.card {
  view-transition-name: card;
}
/* 多个卡片使用相同的名称 */

通过示例：

// 仅为正在过渡的元素分配唯一名称
element.style.viewTransitionName = `card-${id}`;

transition-name-cleanup

transition-name-cleanup

Remove view-transition-name after transition completes.

Fail:

sourceImg.style.viewTransitionName = "card";
document.startViewTransition(() => {
  targetImg.style.viewTransitionName = "card";
});
// sourceImg still has name, causes conflict on next transition

Pass:

sourceImg.style.viewTransitionName = "card";
document.startViewTransition(() => {
  sourceImg.style.viewTransitionName = "";
  targetImg.style.viewTransitionName = "card";
});

过渡完成后需移除view-transition-name属性。

失败示例：

sourceImg.style.viewTransitionName = "card";
document.startViewTransition(() => {
  targetImg.style.viewTransitionName = "card";
});
// sourceImg仍保留该名称，导致下一次过渡时冲突

通过示例：

sourceImg.style.viewTransitionName = "card";
document.startViewTransition(() => {
  sourceImg.style.viewTransitionName = "";
  targetImg.style.viewTransitionName = "card";
});

transition-over-js-library

transition-over-js-library

Prefer View Transitions API over JavaScript animation libraries for page transitions.

Fail:

tsx

import { motion } from "motion/react";

function ImageLightbox() {
  return (
    <motion.img layoutId="hero" /> // JS-based shared element transition
  );
}

Pass:

function openLightbox(img: HTMLImageElement) {
  img.style.viewTransitionName = "hero";
  document.startViewTransition(() => {
    // Native browser transition
  });
}

实现页面过渡时，优先使用View Transitions API而非JavaScript动画库。

失败示例：

tsx

import { motion } from "motion/react";

function ImageLightbox() {
  return (
    <motion.img layoutId="hero" /> // 基于JS的共享元素过渡
  );
}

通过示例：

function openLightbox(img: HTMLImageElement) {
  img.style.viewTransitionName = "hero";
  document.startViewTransition(() => {
    // 浏览器原生过渡
  });
}

transition-style-pseudo-elements

transition-style-pseudo-elements

Style view transition pseudo-elements for custom animations.

Fail:

document.startViewTransition(() => { /* ... */ });
// Uses default crossfade

Pass:

css

::view-transition-group(card) {
  animation-duration: 300ms;
  animation-timing-function: cubic-bezier(0.215, 0.61, 0.355, 1);
}

通过为视图过渡伪元素设置样式实现自定义动画。

失败示例：

document.startViewTransition(() => { /* ... */ });
// 使用默认的淡入淡出效果

通过示例：

css

::view-transition-group(card) {
  animation-duration: 300ms;
  animation-timing-function: cubic-bezier(0.215, 0.61, 0.355, 1);
}

Native Styling Rules

原生样式规则

native-backdrop-styling

native-backdrop-styling

Use ::backdrop pseudo-element for dialog/popover backgrounds.

Fail:

tsx

<>
  <div className={styles.overlay} onClick={close} />
  <dialog className={styles.dialog}>{children}</dialog>
</>

Pass:

css

dialog::backdrop {
  background: var(--black-a6);
  backdrop-filter: blur(4px);
}

使用::backdrop伪元素为dialog/popover设置背景。

失败示例：

tsx

<>
  <div className={styles.overlay} onClick={close} />
  <dialog className={styles.dialog}>{children}</dialog>
</>

通过示例：

css

dialog::backdrop {
  background: var(--black-a6);
  backdrop-filter: blur(4px);
}

native-placeholder-styling

native-placeholder-styling

Use ::placeholder for input placeholder styling, not wrapper elements.

Fail:

tsx

<div className={styles.inputWrapper}>
  {!value && <span className={styles.placeholder}>Enter text...</span>}
  <input value={value} />
</div>

Pass:

css

input::placeholder {
  color: var(--gray-9);
  opacity: 1;
}

使用::placeholder伪元素设置输入框占位符样式，而非额外的容器元素。

失败示例：

tsx

<div className={styles.inputWrapper}>
  {!value && <span className={styles.placeholder}>Enter text...</span>}
  <input value={value} />
</div>

通过示例：

css

input::placeholder {
  color: var(--gray-9);
  opacity: 1;
}

native-selection-styling

native-selection-styling

Use ::selection for text selection styling.

Pass:

css

::selection {
  background: var(--blue-a5);
  color: var(--gray-12);
}

使用::selection伪元素设置文本选中样式。

通过示例：

css

::selection {
  background: var(--blue-a5);
  color: var(--gray-12);
}

Output Format

输出格式

When reviewing files, output findings as:

file:line - [rule-id] description of issue

Example:
components/button/styles.module.css:12 - [pseudo-content-required] ::before missing content property
components/lightbox/index.tsx:45 - [transition-over-js-library] Using motion layoutId instead of View Transitions API

审查文件时，输出结果格式如下：

file:line - [规则ID] 问题描述

示例：
components/button/styles.module.css:12 - [pseudo-content-required] ::before缺少content属性
components/lightbox/index.tsx:45 - [transition-over-js-library] 使用motion layoutId而非View Transitions API

Summary Table

汇总表格

After findings, output a summary:

Rule	Count	Severity
`pseudo-content-required`	2	HIGH
`pseudo-over-dom-node`	1	MEDIUM
`transition-name-cleanup`	1	MEDIUM

输出检查结果后，需生成汇总表：

规则	数量	严重程度
`pseudo-content-required`	2	高
`pseudo-over-dom-node`	1	中
`transition-name-cleanup`	1	中

pseudo-elements

Original

Translation

Pseudo Elements

Pseudo Elements

How It Works

工作原理

Rule Categories

规则分类

Rules

规则

Before/After Rules

Before/After 规则

pseudo-content-required

pseudo-content-required

pseudo-over-dom-node

pseudo-over-dom-node

pseudo-position-relative-parent

pseudo-position-relative-parent

pseudo-z-index-layering

pseudo-z-index-layering

pseudo-hit-target-expansion

pseudo-hit-target-expansion

View Transitions Rules

View Transitions 规则

transition-name-required

transition-name-required

transition-name-unique

transition-name-unique

transition-name-cleanup

transition-name-cleanup

transition-over-js-library

transition-over-js-library

transition-style-pseudo-elements

transition-style-pseudo-elements

Native Styling Rules

原生样式规则

native-backdrop-styling

native-backdrop-styling

native-placeholder-styling

native-placeholder-styling

native-selection-styling

native-selection-styling

Output Format

输出格式

Summary Table

汇总表格

References

参考资料

`pseudo-content-required`

`pseudo-content-required`

`pseudo-over-dom-node`

`pseudo-over-dom-node`

`pseudo-position-relative-parent`

`pseudo-position-relative-parent`

`pseudo-z-index-layering`

`pseudo-z-index-layering`

`pseudo-hit-target-expansion`

`pseudo-hit-target-expansion`

`transition-name-required`

`transition-name-required`

`transition-name-unique`

`transition-name-unique`

`transition-name-cleanup`

`transition-name-cleanup`

`transition-over-js-library`

`transition-over-js-library`

`transition-style-pseudo-elements`

`transition-style-pseudo-elements`

`native-backdrop-styling`

`native-backdrop-styling`

`native-placeholder-styling`

`native-placeholder-styling`

`native-selection-styling`

`native-selection-styling`