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_Primitive_Data.md

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+---
+id: javascript-primitive-data-types
+title: "JavaScript Primitive Data Types"
+category: "Frontend"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["JS primitives", "primitive types", "string number boolean", "undefined null", "BigInt"]
+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: ["javascript", "js", "web", "frontend", "w3schools", "primitives", "data-types", "string", "number"]
+raw_sources: ["https://www.w3schools.com/js/js_datatypes_primitives.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[JavaScript Primitive Data Types]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+JavaScript has 7 primitive data types — Number, BigInt, String, Boolean, Undefined, Null, and Symbol — each a simple, immutable value distinct from the single object type. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **7 primitive types** — JavaScript variables can hold 7 primitive types (Number, BigInt, String, Boolean, Undefined, Null, Symbol) or 1 object type. [S1]
+- **Strings** — a string is a series of characters, written with single or double quotes. [S1]
+- **Numbers are 64-bit floats** — all JavaScript numbers are stored as double (64-bit floating point) values; they support decimals and exponential notation. [S1]
+- **BigInt (ES2020)** — handles integers too large for standard numbers. [S1]
+- **Undefined vs Null** — a variable without a value is `undefined`; `null` represents the intentional absence of a value, but `typeof null` returns `"object"` (a historical quirk). [S1]
+
+## 🧩 추출된 패턴 (Extracted patterns)
+- **Nest opposite quotes** — put single quotes inside double-quoted strings (and vice versa) to avoid escaping. [S1]
+- **`===` vs `==` for null/undefined** — strict equality (`===`) is `true` only when value and type match; loose equality (`==`) treats `null` and `undefined` as equal. [S1]
+- **Empty string is still a string** — `let car = "";` has value `""` and `typeof "string"`. [S1]
+
+## 📖 세부 내용 (Details)
+JavaScript variables can hold 8 types of data: 7 primitive types or 1 object type. The primitive types are: Number, BigInt, String, Boolean, Undefined, Null, and Symbol. [S1]
+
+**JavaScript Strings**
+A string is a series of characters like "John Doe", written with single or double quotes. [S1]
+```javascript
+// Using double quotes:
+let carName1 = "Volvo XC60";
+
+// Using single quotes:
+let carName2 = 'Volvo XC60';
+```
+You can nest the opposite quote type inside a string: [S1]
+```javascript
+// Single quote inside double quotes:
+let answer1 = "It's alright";
+
+// Single quotes inside double quotes:
+let answer2 = "He is called 'Johnny'";
+
+// Double quotes inside single quotes:
+let answer3 = 'He is called "Johnny"';
+```
+
+**JavaScript Numbers**
+All JavaScript numbers are stored as decimal (floating point) values — always double (64-bit floating point). [S1]
+```javascript
+// With decimals:
+let x1 = 34.00;
+
+// Without decimals:
+let x2 = 34;
+```
+Exponential notation: [S1]
+```javascript
+let y = 123e5;    // 12300000
+let z = 123e-5;   // 0.00123
+```
+
+**JavaScript BigInt**
+BigInt (ES2020) handles integers too large for standard numbers: [S1]
+```javascript
+let x = BigInt("123456789012345678901234567890");
+```
+
+**JavaScript Booleans**
+Booleans can only hold `true` or `false`: [S1]
+```javascript
+let x = 5;
+let y = 5;
+let z = 6;
+(x == y)       // Returns true
+(x == z)       // Returns false
+```
+
+**The `typeof` Operator**
+The `typeof` operator identifies a variable's type. [S1]
+```javascript
+typeof ""             // Returns "string"
+typeof "John"         // Returns "string"
+typeof "John Doe"     // Returns "string"
+```
+```javascript
+typeof 0              // Returns "number"
+typeof 314            // Returns "number"
+typeof 3.14           // Returns "number"
+typeof (3)            // Returns "number"
+typeof (3 + 4)        // Returns "number"
+```
+
+**Undefined**
+A variable without a value has the value `undefined` and the type `undefined`: [S1]
+```javascript
+let car;    // Value is undefined, type is undefined
+```
+```javascript
+car = undefined;    // Value is undefined, type is undefined
+```
+
+**Empty Values**
+An empty string has both a legal value and a type: [S1]
+```javascript
+let car = "";    // The value is "", the typeof is "string"
+```
+
+**Datatype null**
+`null` represents "nothing" — the intentional absence of a value: [S1]
+```javascript
+let carName = null;
+```
+Notes on `null`: the `typeof` operator returns `"object"` for `null` (a historical quirk); the strict equality operator `===` returns `true` only if both value and type match; the loose equality operator `==` returns `true` for both `null` and `undefined`. [S1]
+
+## 🛠️ 적용 사례 (Applied in summary)
+The page's own declarations (string quoting variants, number/exponent/BigInt literals, boolean comparisons, and the undefined/empty/null examples) are the canonical applied examples. No external project/commit applications found in the source.
+
+## 💻 코드 패턴 (Code patterns)
+Nest opposite quotes (language: JavaScript):
+```javascript
+let answer1 = "It's alright";
+let answer3 = 'He is called "Johnny"';
+```
+Exponential number notation:
+```javascript
+let y = 123e5;    // 12300000
+let z = 123e-5;   // 0.00123
+```
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+`typeof null` returns `"object"` even though `null` is a primitive value — the page flags this as a historical quirk. BigInt was introduced in ES2020. [S1]
+
+## ✅ 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:** [[JavaScript Tutorial]]
+- **관련 개념:** [[JavaScript Data Types]], [[JavaScript Object Data Types]], [[JavaScript typeof]], [[JavaScript Symbols]]
+- **참조 맥락:** Referenced whenever declaring simple values or reasoning about equality and `typeof` results.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — JavaScript Primitive Data Types — https://www.w3schools.com/js/js_datatypes_primitives.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript Primitive Data Types" page (Astra wiki-curation, P-Reinforce v3.1 format).