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_Loops.md

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+---
+id: javascript-loops
+title: "JavaScript Loops"
+category: "Frontend"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["loops", "JS loops", "for loop", "while loop", "do while", "iteration"]
+duplicate_of: ""
+source_trust_level: "B"
+confidence_score: 0.88
+created_at: 2026-06-23
+updated_at: 2026-06-23
+review_reason: ""
+merge_history: []
+tags: ["javascript", "js", "web", "frontend", "w3schools", "loops", "iteration", "control-flow"]
+raw_sources: ["https://www.w3schools.com/js/js_loops.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[JavaScript Loops]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+Loops let you run the same block of code many times, each time with a different value — replacing long repetitive sequences with a compact iteration. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **Loops repeat a block of code** — they execute a code block multiple times, often with a different value each pass. [S1]
+- **`for` loop** — uses three expressions: an initializer, a condition, and an update run after each iteration. [S1]
+- **`while` loop** — runs as long as a specified condition is true. [S1]
+- **`do/while` loop** — a variant that runs the block at least once before checking the condition. [S1]
+- **Loop scope** — variables declared with `let` inside a loop are visible only within the loop, unlike `var`. [S1]
+- **Infinite-loop hazard** — forgetting to update the condition variable means the loop never ends and crashes the browser. [S1]
+
+## 🧩 추출된 패턴 (Extracted patterns)
+- **Replace repetition with iteration** — instead of writing the same statement for each array index, loop over `cars.length`. [S1]
+- **Index accumulation** — append each iteration's value into a result string (`text += ...`). [S1]
+- **Always advance the condition variable** — increment (e.g. `i++`) so the condition eventually becomes false. [S1]
+
+## 📖 세부 내용 (Details)
+**Why loops** [S1]
+Loops are handy if you want to run the same code over and over again, each time with a different value. Instead of writing the same statement many times:
+```javascript
+text += cars[0] + "<br>";
+text += cars[1] + "<br>";
+text += cars[2] + "<br>";
+text += cars[3] + "<br>";
+text += cars[4] + "<br>";
+text += cars[5] + "<br>";
+```
+You can write:
+```javascript
+for (let i = 0; i < cars.length; i++) {
+  text += cars[i] + "<br>";
+}
+```
+
+**The `for` loop** [S1]
+The `for` loop has the syntax `for (expr1; expr2; expr3) { // code block to be executed }`.
+```javascript
+for (let i = 0; i < 5; i++) {
+  text += "The number is " + i + "<br>";
+}
+```
+
+**Loop scope — `var` vs `let`** [S1]
+Using `var` in a loop, the loop variable redeclares the outer variable:
+```javascript
+let i = 5;
+
+for (i = 0; i < 10; i++) {
+  // some code
+}
+
+// Here i is 10
+```
+Using `let` in a loop, the loop variable is scoped only to the loop:
+```javascript
+let i = 5;
+
+for (let i = 0; i < 10; i++) {
+  // some code
+}
+
+// Here i is 5
+```
+
+**The `while` loop** [S1]
+The `while` loop has the syntax `while (condition) { // code block to be executed }`.
+```javascript
+while (i < 10) {
+  text += "The number is " + i;
+  i++;
+}
+```
+Note: If you forget to increase the variable used in the condition, the loop will never end. This will crash your browser.
+
+**The `do/while` loop** [S1]
+The `do/while` loop has the syntax `do { // code block to be executed } while (condition);`.
+```javascript
+do {
+  text += "The number is " + i;
+  i++;
+}
+while (i < 10);
+```
+Note: The `do while` runs at least once, even if the condition is false from the start.
+
+**Different kinds of loops** [S1]
+JavaScript supports the `for` loop (loops through a block of code a number of times), the `for/in` loop (loops through the properties of an object), the `for/of` loop (loops through the values of an iterable object), the `while` loop (loops through a block of code while a condition is true), and the `do/while` loop (also loops while a condition is true).
+
+## 🛠️ 적용 사례 (Applied in summary)
+The page's own snippets are the canonical applied examples — replacing repeated `text += cars[n]` statements with a `for` loop over `cars.length`, and accumulating numbers in `for`/`while`/`do-while` loops. No external project/commit applications found in the source.
+
+## 💻 코드 패턴 (Code patterns)
+Iterate an array:
+```javascript
+for (let i = 0; i < cars.length; i++) {
+  text += cars[i] + "<br>";
+}
+```
+While loop with advancing counter:
+```javascript
+while (i < 10) {
+  text += "The number is " + i;
+  i++;
+}
+```
+Do-while (runs at least once):
+```javascript
+do {
+  text += "The number is " + i;
+  i++;
+}
+while (i < 10);
+```
+
+## ⚖️ 비교 및 선택 기준 (Comparison & decision criteria)
+- **`for` vs `while`** — use `for` when the number of iterations / the counter is known up front (init, condition, update in one place); use `while` when looping purely on a condition. [S1]
+- **`while` vs `do/while`** — use `do/while` when the block must run at least once even if the condition is initially false. [S1]
+- **`let` vs `var` for the loop variable** — `let` keeps the counter scoped to the loop; `var` leaks it to the surrounding scope. [S1]
+
+## ⚖️ 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:** 0.88
+- **중복 검사 결과:** 신규 생성 (New discovery)
+
+## 🔗 지식 그래프 (Knowledge Graph)
+- **상위/루트:** [[JavaScript Tutorial]]
+- **관련 개념:** [[JavaScript For Loop]], [[JavaScript While Loop]], [[JavaScript Break]], [[JavaScript Booleans]]
+- **참조 맥락:** The overview entry point for all iteration constructs; specific loop types are detailed in their own pages.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — JavaScript Loops — https://www.w3schools.com/js/js_loops.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript Loops" page (Astra wiki-curation, P-Reinforce v3.1 format).