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>
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id: javascript-break
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title: "JavaScript Break"
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category: "Frontend"
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status: "draft"
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verification_status: "conceptual"
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canonical_id: ""
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aliases: ["break statement", "JS break", "labeled break", "break continue", "break label"]
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duplicate_of: ""
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source_trust_level: "B"
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confidence_score: 0.89
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created_at: 2026-06-23
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updated_at: 2026-06-23
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review_reason: ""
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merge_history: []
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tags: ["javascript", "js", "web", "frontend", "w3schools", "break", "loops", "labels", "control-flow"]
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raw_sources: ["https://www.w3schools.com/js/js_break.asp"]
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applied_in: []
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github_commit: ""
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---
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# [[JavaScript Break]]
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## 🎯 한 줄 통찰 (One-line insight)
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The `break` statement jumps out of a loop or switch; with a label, it can jump out of any code block. [S1]
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## 🧠 핵심 개념 (Core concepts)
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- **Jumps out** — the `break` statement "jumps out" of loops and switches, terminating execution immediately. [S1]
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- **Break in loops** — when `break` is reached in a loop, the loop terminates immediately and control transfers to the statements following the loop; no further iterations execute. [S1]
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- **Break in a switch** — in a `switch`, `break` exits the block after a matching case executes; without it, execution falls through to subsequent cases. [S1]
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- **Labels** — a label is an identifier followed by a colon (`labelname: statement;`), and `break labelname;` jumps out of the labeled block. [S1]
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- **Only break and continue jump out of a block** — `break` and `continue` are the only JavaScript statements that can jump out of a code block; without a label, `break` only exits loops or switches. [S1]
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## 🧩 추출된 패턴 (Extracted patterns)
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- **Early exit on a sentinel** — test a condition inside the loop and `break` when it is met. [S1]
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- **Labeled break for nested loops** — name outer/inner loops and `break loop1;` / `break loop2;` to control exactly which loop terminates. [S1]
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- **Break out of a plain code block** — label a `{ ... }` block and `break label;` to skip the remaining statements. [S1]
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## 📖 세부 내용 (Details)
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**The break statement** [S1]
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The `break` statement "jumps out" of loops and switches, terminating execution of a loop or switch statement immediately.
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**Break in loops** [S1]
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When `break` is encountered in a loop, the loop terminates immediately and control transfers to the statements following the loop. No further iterations execute.
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```javascript
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for (let i = 0; i < 10; i++) {
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if (i === 3) { break; }
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text += "The number is " + i + "<br>";
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}
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```
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**Break in a switch** [S1]
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In a `switch` statement, `break` exits the block after a matching case executes. Without it, execution "falls through" to subsequent cases.
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```javascript
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switch (new Date().getDay()) {
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case 0:
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day = "Sunday";
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break;
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case 1:
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day = "Monday";
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break;
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case 2:
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day = "Tuesday";
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break;
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case 3:
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day = "Wednesday";
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break;
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case 4:
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day = "Thursday";
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break;
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case 5:
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day = "Friday";
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break;
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case 6:
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day = "Saturday";
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}
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```
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**JavaScript labels** [S1]
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A label is an identifier followed by a colon: `labelname: statement;`. A labeled break uses the syntax `break labelname;`.
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**Break to loop1** [S1]
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```javascript
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let text = "";
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loop1: for (let j = 1; j < 5; j++) {
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loop2: for (let i = 1; i < 5; i++) {
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if (i === 3) { break loop1; }
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text += i;
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}
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}
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```
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**Break to loop2** [S1]
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```javascript
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let text = "";
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loop1: for (let j = 1; j < 5; j++) {
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loop2: for (let i = 1; i < 5; i++) {
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if (i === 3) { break loop2; }
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text += i;
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}
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}
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```
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**Break out of a code block** [S1]
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```javascript
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const cars = ["BMW", "Volvo", "Saab", "Ford"];
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list: {
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text += cars[0] + "<br>";
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text += cars[1] + "<br>";
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break list;
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text += cars[2] + "<br>";
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text += cars[3] + "<br>";
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}
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```
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**Note** [S1]
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`break` and `continue` are the only JavaScript statements that can "jump out of" a code block. Without a label, `break` only exits loops or switches; with a label, it exits any code block.
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## 🛠️ 적용 사례 (Applied in summary)
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The page's own snippets are the canonical applied examples — early-exiting a `for` loop at `i === 3`, exiting `switch` cases, labeled breaks targeting `loop1`/`loop2`, and breaking out of a labeled `list:` block. No external project/commit applications found in the source.
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## 💻 코드 패턴 (Code patterns)
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Early exit from a loop:
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```javascript
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for (let i = 0; i < 10; i++) {
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if (i === 3) { break; }
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text += "The number is " + i + "<br>";
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}
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```
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Labeled break out of an outer loop:
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```javascript
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loop1: for (let j = 1; j < 5; j++) {
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loop2: for (let i = 1; i < 5; i++) {
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if (i === 3) { break loop1; }
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text += i;
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}
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}
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```
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Break out of a labeled code block:
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```javascript
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list: {
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text += cars[0] + "<br>";
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break list;
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text += cars[2] + "<br>";
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}
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```
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## ⚖️ 모순 및 업데이트 (Contradictions & updates)
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No contradictions found in the source.
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## ✅ 검증 상태 및 신뢰도
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- **상태:** draft
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- **검증 단계:** conceptual (실제 적용 사례 발견 시 applied/validated로 승격 가능)
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- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
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- **신뢰 점수:** 0.89
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- **중복 검사 결과:** 신규 생성 (New discovery)
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## 🔗 지식 그래프 (Knowledge Graph)
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- **상위/루트:** [[JavaScript Tutorial]]
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- **관련 개념:** [[JavaScript Loops]], [[JavaScript For Loop]], [[JavaScript While Loop]], [[JavaScript Switch]]
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- **참조 맥락:** Used to terminate loops/switches early; paired with `continue` as the only block-jumping statements.
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## 📚 출처 (Sources)
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- [S1] W3Schools — JavaScript Break — https://www.w3schools.com/js/js_break.asp
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## 📝 변경 이력 (Change history)
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- 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript Break" page (Astra wiki-curation, P-Reinforce v3.1 format).
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