docs(10_Wiki): W3Schools 위키화 — HTML/CSS/JavaScript(core)

W3Schools 튜토리얼을 P-Reinforce v3.1 포맷으로 위키화(영어 본문, 한/영 섹션 헤더). - Topic_HTML: 59문서 (튜토리얼+예제, 레퍼런스/메타 제외) - Topic_CSS: 190문서 (메인 + Advanced/Flexbox/Grid/RWD 전체) - Topic_JavaScript: 120문서 (코어 언어; Temporal/DOM상세/BOM/WebAPI/AJAX/jQuery/Graphics 등은 후속) 각 폴더 00_INDEX.md(MOC) 포함. 코드 verbatim, 미확인분은 "Not found in source" 표기. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-23 19:21:18 +09:00
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+---
+id: css-counters
+title: "CSS Counters"
+category: "Frontend"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["CSS counters", "counter-reset", "counter-increment", "automatic numbering", "counter() function"]
+duplicate_of: ""
+source_trust_level: "B"
+confidence_score: 0.89
+created_at: 2026-06-23
+updated_at: 2026-06-23
+review_reason: ""
+merge_history: []
+tags: ["css", "web", "frontend", "w3schools", "counters", "generated-content"]
+raw_sources: ["https://www.w3schools.com/css/css_counters.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[CSS Counters]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+CSS counters are "variables" maintained by CSS whose values can be incremented (or decremented) by CSS rules, enabling automatic numbering of elements like section headings — no JavaScript required. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **What counters are** — CSS counters are "variables" maintained by CSS, and their values can be incremented (or decremented) by CSS rules. [S1]
+- **`counter-reset`** — creates or resets a counter. [S1]
+- **`counter-increment`** — increments (or decrements) a counter value. [S1]
+- **`content`** — inserts generated content (used with `::before`/`::after`). [S1]
+- **`counter()`** — adds/returns the value of a named counter to an element. [S1]
+- **Increment direction & amount** — `counter-increment` takes a second parameter (default 1); a negative value decrements, and any value can be used to step by more than 1. [S1]
+
+## 🧩 추출된 패턴 (Extracted patterns)
+- **Reset on container, increment on item** — set `counter-reset` on a container (e.g., `body`) and `counter-increment` on the repeated element's `::before`. [S1]
+- **Compose generated labels** — combine string literals with `counter(name)` inside `content` to produce labels like `"Section 1: "`. [S1]
+- **Tune the step** — change numbering direction/granularity purely by the second argument of `counter-increment` (e.g., `-1`, `2`). [S1]
+
+## 📖 세부 내용 (Details)
+**CSS Automatic Numbering With Counters**
+CSS counters are "variables" maintained by CSS, and their values can be incremented (or decremented) by CSS rules. The properties/functions used are: `counter-reset` (creates or resets a counter), `counter-increment` (increments/decrements a counter value), `content` (inserts generated content), and `counter()` (adds the value of a counter to an element). [S1]
+
+**CSS Increase and Decrease Counter**
+The following example creates a counter for the page (in the `body` selector), then increments the counter value by 1 for each `<h2>` element, adding `"Section <value>: "` before each `<h2>`: [S1]
+```css
+body {
+  counter-reset: section;
+}
+
+h2::before {
+  counter-increment: section;
+  content: "Section " counter(section) ": ";
+}
+```
+
+**Decrementing a Counter**
+The `counter-increment` property has a second parameter. The default value is 1. To decrease the counter value, you can set it to -1: [S1]
+```css
+body {
+  counter-reset: section;
+}
+
+h2::before {
+  counter-increment: section -1;
+  content: "Section " counter(section) ": ";
+}
+```
+
+**Incrementing by Custom Values**
+You can increment the counter by any value. Here we increment by 2: [S1]
+```css
+body {
+  counter-reset: section;
+}
+
+h2::before {
+  counter-increment: section 2;
+  content: "Section " counter(section) ": ";
+}
+```
+
+## 🛠️ 적용 사례 (Applied in summary)
+The page's examples are the applied cases: numbering `<h2>` headings as "Section 1:", "Section 2:", etc., plus variants that decrement (`-1`) and step by 2. No external project/commit applications found in the source.
+
+## 💻 코드 패턴 (Code patterns)
+Basic auto-numbering (language: CSS):
+```css
+body {
+  counter-reset: section;
+}
+
+h2::before {
+  counter-increment: section;
+  content: "Section " counter(section) ": ";
+}
+```
+Custom step (language: CSS):
+```css
+h2::before {
+  counter-increment: section 2;
+}
+```
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+No contradictions found in the source.
+
+## ✅ 검증 상태 및 신뢰도
+- **상태:** draft
+- **검증 단계:** conceptual (실제 적용 사례 발견 시 applied/validated로 승격 가능)
+- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
+- **신뢰 점수:** 0.89
+- **중복 검사 결과:** 신규 생성 (New discovery)
+
+## 🔗 지식 그래프 (Knowledge Graph)
+- **상위/루트:** [[CSS Tutorial]]
+- **관련 개념:** [[CSS Nested Counters]], [[CSS Pseudo-elements]], [[CSS Lists]]
+- **참조 맥락:** Referenced when generating automatic numbering for headings, lists, or sections without scripting.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — CSS Counters — https://www.w3schools.com/css/css_counters.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-06-23: Initial draft synthesized from the W3Schools "CSS Counters" page (Astra wiki-curation, P-Reinforce v3.1 format).