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>

10_Wiki/Topic_JavaScript/JavaScript_Sets.md

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+---
+id: javascript-sets
+title: "JavaScript Sets"
+category: "Frontend"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["Set", "new Set", "unique values", "ES6 Set", "Set add", "Set collection"]
+duplicate_of: ""
+source_trust_level: "B"
+confidence_score: 0.9
+created_at: 2026-06-23
+updated_at: 2026-06-23
+review_reason: ""
+merge_history: []
+tags: ["javascript", "js", "web", "frontend", "w3schools", "set", "collection", "es6"]
+raw_sources: ["https://www.w3schools.com/js/js_sets.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[JavaScript Sets]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+A JavaScript Set is a collection of unique values — each value can occur only once — built either from an array or by adding values one at a time, and iterable with `for...of`. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **A Set is a collection of unique values.** Each value can only occur once in a Set, and values can be of any type — primitive values or objects. [S1]
+- **Two ways to create a Set** — pass an array to `new Set()`, or create an empty `new Set()` and use `add()`. [S1]
+- **`add()` ignores duplicates** — adding a value that already exists has no effect; only the first occurrence is retained. [S1]
+- **Sets are iterable** — a `for...of` loop lists all elements. [S1]
+- **Type identity** — `typeof` a Set returns `"object"`, and `instanceof Set` returns `true`. [S1]
+- **Set is an ES6 feature** with full support in all modern browsers since June 2017. [S1]
+
+## 🧩 추출된 패턴 (Extracted patterns)
+- **Deduplicate by construction** — feeding values into a Set automatically discards repeats. [S1]
+- **Empty-then-populate** — `const s = new Set();` followed by repeated `s.add(...)`. [S1]
+- **Add variables, not just literals** — `add()` accepts any value, including variables holding objects. [S1]
+
+## 📖 세부 내용 (Details)
+A JavaScript Set is a collection of unique values. Each value can only occur once in a Set. The values can be of any type, primitive values or objects. [S1]
+
+**How to create a Set** — you can create a JavaScript Set by passing an array to `new Set()`, or create an empty Set and add values. [S1]
+
+**The new Set() Method** — pass an array to the `new Set()` constructor: [S1]
+```javascript
+// Create a Set
+const letters = new Set(["a","b","c"]);
+```
+
+Create an empty Set and add values with `add()`: [S1]
+```javascript
+// Create a Set
+const letters = new Set();
+
+// Add Values to the Set
+letters.add("a");
+letters.add("b");
+letters.add("c");
+```
+
+You can add variables to a Set: [S1]
+```javascript
+// Create a Set
+const letters = new Set();
+
+// Create Variables
+const a = "a";
+const b = "b";
+const c = "c";
+
+// Add Variables to the Set
+letters.add(a);
+letters.add(b);
+letters.add(c);
+```
+
+**The add() Method** [S1]
+```javascript
+letters.add("d");
+letters.add("e");
+```
+
+If you add equal elements, only the first will be saved: [S1]
+```javascript
+letters.add("a");
+letters.add("b");
+letters.add("c");
+letters.add("c");
+letters.add("c");
+letters.add("c");
+letters.add("c");
+letters.add("c");
+```
+
+**Listing the Elements** — you can list all the elements of a Set with a `for...of` loop: [S1]
+```javascript
+// Create a Set
+const letters = new Set(["a","b","c"]);
+
+// List all Elements
+let text = "";
+for (const x of letters) {
+  text += x;
+}
+```
+
+**A JavaScript Set is an Object** [S1]
+```javascript
+typeof letters;      // Returns object
+```
+```javascript
+letters instanceof Set;  // Returns true
+```
+
+**Browser Support** — Set is an ES6 feature (JavaScript 2015), fully supported in all modern browsers since June 2017. [S1]
+
+| Browser | Version | Release |
+|---------|---------|---------|
+| Chrome | 51 | May 2016 |
+| Edge | 15 | Apr 2017 |
+| Firefox | 54 | Jun 2017 |
+| Safari | 10 | Sep 2016 |
+| Opera | 38 | Jun 2016 |
+
+## 🛠️ 적용 사례 (Applied in summary)
+The page's own snippets are the canonical applied examples — building a `letters` Set from an array or by adding values, demonstrating that duplicate `add()` calls collapse to one, and listing elements with `for...of`. No external project/commit applications found in the source.
+
+## 💻 코드 패턴 (Code patterns)
+Create a Set from an array (language: JavaScript):
+```javascript
+const letters = new Set(["a","b","c"]);
+```
+Iterate a Set:
+```javascript
+let text = "";
+for (const x of letters) {
+  text += x;
+}
+```
+
+## ⚖️ 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:** 0.90
+- **중복 검사 결과:** 신규 생성 (New discovery)
+
+## 🔗 지식 그래프 (Knowledge Graph)
+- **상위/루트:** [[JavaScript Tutorial]]
+- **관련 개념:** [[JavaScript Set Methods]], [[JavaScript Set Logic]], [[JavaScript Maps]]
+- **참조 맥락:** The base concept referenced whenever a collection of unique values is needed.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — JavaScript Sets — https://www.w3schools.com/js/js_sets.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript Sets" page (Astra wiki-curation, P-Reinforce v3.1 format).