refactor(topics): 멀티 에이전트용 지식 재편 — _Common(공통 기본기) + Domain_* 구조
에이전트 8종(대화형/프로그래머 C·S/디자이너/설계자/기획자/QA/PD/PM)에게 [공통 기본 능력 + 롤별 Specialty] 2층으로 지식을 주입하기 위한 재분류. 문서 내용·포맷은 무수정, 폴더 이동만 (6,372개 문서 수 보존 확인). - Topic_Programming → Domain_Programming (내부 구조 보존) - Topic_Graphic → Domain_Design - Topic_Business → Domain_Product - Topic_General → Domain_General - _Common 신설: Math(구 Topic_Math_Specialty), Reasoning(구 General/From_Thinking & Reasoning), Reasoning_Creativity(구 General/From_창의성), Communication(Poetic_Blog_Writing + From_writing) - 타 도메인의 From_* 폴더는 유지 (출처 표기일 뿐, 이미 도메인에 맞게 분류된 문서) - 빈 폴더 정리 (memory/procedures) - 에이전트→폴더 매핑은 workspace의 .astra/agent-knowledge-map.json (9개 에이전트) Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Antigravity Agent
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---
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id: javascript-nan
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title: "JavaScript NaN"
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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: ["NaN", "Not a Number", "JS NaN", "isNaN", "invalid number"]
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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", "nan", "numbers"]
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raw_sources: ["https://www.w3schools.com/js/js_nan.asp"]
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applied_in: []
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github_commit: ""
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---
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# [[JavaScript NaN]]
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## 🎯 한 줄 통찰 (One-line insight)
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`NaN` ("Not a Number") is a JavaScript number-type value produced when a calculation cannot yield a valid number, and it is the only JavaScript value that is not equal to itself. [S1]
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## 🧠 핵심 개념 (Core concepts)
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- **Produced by invalid math** — You get `NaN` when JavaScript cannot calculate a number (e.g. `100 / "Apple"`). [S1]
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- **Its type is `number`** — The type of `NaN` is `number`; though it means "not a number," it belongs to the JavaScript number type. [S1]
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- **Numeric strings convert** — JavaScript tries to convert numeric strings to numbers in arithmetic operations, so `100 / "10"` is `10`. [S1]
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- **Non-numeric strings yield NaN** — A non-numeric string cannot be converted to a number, so the result is `NaN`. [S1]
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- **`isNaN()` detects it** — Use the `isNaN()` function to find out if a value is not a number. [S1]
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- **Not equal to itself** — `NaN` is the only JavaScript value that is not equal to itself; `NaN == NaN` is `false`. [S1]
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- **Propagates through math** — If you use `NaN` in a mathematical operation, the result will also be `NaN`. [S1]
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## 🧩 추출된 패턴 (Extracted patterns)
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- **Never compare with `==`** — Because `NaN != NaN`, test for it with `isNaN()` rather than equality. [S1]
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- **Coerce-then-compute** — Arithmetic implicitly coerces string operands to numbers; convertible strings work, non-convertible ones poison the result with `NaN`. [S1]
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- **NaN contamination** — Any arithmetic involving `NaN` returns `NaN`, so a single bad value can spread through a calculation chain. [S1]
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## 📖 세부 내용 (Details)
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**Invalid Number Operations**
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You get `NaN` when JavaScript cannot calculate a number. [S1]
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```javascript
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let x = 100 / "Apple";
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document.getElementById("demo").innerHTML = x;
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```
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**NaN is a Number**
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The type of `NaN` is `number`. This may look strange, but `NaN` belongs to the JavaScript number type. [S1]
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```javascript
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let x = NaN;
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document.getElementById("demo").innerHTML = typeof x;
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```
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**Numeric Strings**
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JavaScript tries to convert numeric strings to numbers in arithmetic operations. The result is `10`, because `"10"` is converted to the number `10`. [S1]
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```javascript
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let x = 100 / "10";
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document.getElementById("demo").innerHTML = x;
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```
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**Non-Numeric Strings**
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A non-numeric string cannot be converted to a number. The result is `NaN`, because `"Apple"` cannot be converted to a number. [S1]
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```javascript
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let x = 100 / "Apple";
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document.getElementById("demo").innerHTML = x;
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```
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**Using isNaN()**
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You can use the JavaScript function `isNaN()` to find out if a value is not a number. [S1]
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```javascript
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let x = 100 / "Apple";
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document.getElementById("demo").innerHTML = isNaN(x);
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```
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**NaN is Not Equal to Itself**
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`NaN` is the only JavaScript value that is not equal to itself. To test for `NaN`, use `isNaN()`. [S1]
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```javascript
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let x = NaN;
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document.getElementById("demo").innerHTML = x == x;
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```
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**NaN in Math**
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If you use `NaN` in a mathematical operation, the result will also be `NaN`. [S1]
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```javascript
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let x = NaN;
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let y = 5;
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document.getElementById("demo").innerHTML = x + y;
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```
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**Note**
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`NaN` means "Not a Number." However, the type of `NaN` is `number`. Use `isNaN()` to check if a value is `NaN`. [S1]
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## 🛠️ 적용 사례 (Applied in summary)
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The page's own snippets are the canonical applied examples — `100 / "Apple"` producing `NaN`, `typeof NaN` returning `"number"`, and `isNaN(x)` testing the result. No external project/commit applications found in the source.
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## 💻 코드 패턴 (Code patterns)
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Test whether a value is NaN (language: JavaScript):
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```javascript
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let x = 100 / "Apple";
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document.getElementById("demo").innerHTML = isNaN(x);
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```
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Observe that NaN is not equal to itself:
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```javascript
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let x = NaN;
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document.getElementById("demo").innerHTML = x == x;
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```
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## ⚖️ 모순 및 업데이트 (Contradictions & updates)
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No contradictions found in the source. (Note the deliberate counter-intuitive facts the page calls out: `typeof NaN` is `"number"`, and `NaN == NaN` is `false`.)
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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 undefined]], [[JavaScript Type Coercion]], [[JavaScript Type Conversion]], [[JavaScript Introduction]]
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- **참조 맥락:** Referenced whenever validating numeric input or guarding arithmetic against invalid values.
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## 📚 출처 (Sources)
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- [S1] W3Schools — JavaScript NaN — https://www.w3schools.com/js/js_nan.asp
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## 📝 변경 이력 (Change history)
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- 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript NaN" page (Astra wiki-curation, P-Reinforce v3.1 format).
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