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_Arithmetic.md

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+---
+id: javascript-arithmetic
+title: "JavaScript Arithmetic"
+category: "Frontend"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["JS arithmetic", "arithmetic operators", "operator precedence", "modulus operator", "exponentiation operator", "increment decrement"]
+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", "arithmetic", "operators"]
+raw_sources: ["https://www.w3schools.com/js/js_arithmetic.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[JavaScript Arithmetic]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+Arithmetic operators perform arithmetic on numbers (literals or variables), with multiplication and division taking higher precedence than addition and subtraction. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **Arithmetic on numbers** — arithmetic operators perform arithmetic on numbers, which can be literals or variables. [S1]
+- **Operands and operators** — the numbers in an arithmetic operation are called operands; the operation performed between two operands is defined by an operator. [S1]
+- **Eight arithmetic operators** — `+`, `-`, `*`, `**`, `/`, `%`, `++`, `--`. [S1]
+- **Modulus returns the remainder** — the modulus operator `%` returns the division remainder. [S1]
+- **Exponentiation equals Math.pow** — `x ** y` produces the same result as `Math.pow(x, y)`. [S1]
+- **Precedence and left-to-right** — multiplication and division have higher precedence than addition and subtraction; operations of equal precedence are computed left to right; parentheses override precedence. [S1]
+
+## 🧩 추출된 패턴 (Extracted patterns)
+- **Operate over literals or variables** — the operands of an arithmetic expression can be literals (`100 + 50`), variables (`a + b`), or sub-expressions (`(100 + 50) * a`). [S1]
+- **Increment/decrement in place** — `x++` raises and `x--` lowers a variable by one. [S1]
+- **Force evaluation order with parentheses** — wrap a lower-precedence operation in `()` to make it run first. [S1]
+
+## 📖 세부 내용 (Details)
+**JavaScript Arithmetic Operators** [S1]
+Arithmetic operators perform arithmetic on numbers (literals or variables):
+
+| Operator | Description |
+|----------|-------------|
+| + | Addition |
+| - | Subtraction |
+| * | Multiplication |
+| ** | Exponentiation (ES2016) |
+| / | Division |
+| % | Modulus (Remainder) |
+| ++ | Increment |
+| -- | Decrement |
+
+**Arithmetic Operations** [S1]
+A typical arithmetic operation operates on two numbers. The two numbers can be literals:
+```javascript
+let x = 100 + 50;
+```
+or variables:
+```javascript
+let x = a + b;
+```
+or expressions:
+```javascript
+let x = (100 + 50) * a;
+```
+
+**Operators and Operands** [S1]
+The numbers (in an arithmetic operation) are called operands. The operation (to be performed between the two operands) is defined by an operator.
+
+**Adding** [S1]
+```javascript
+let x = 5;
+let y = 2;
+let z = x + y;
+```
+
+**Subtracting** [S1]
+```javascript
+let x = 5;
+let y = 2;
+let z = x - y;
+```
+
+**Multiplying** [S1]
+```javascript
+let x = 5;
+let y = 2;
+let z = x * y;
+```
+
+**Dividing** [S1]
+```javascript
+let x = 5;
+let y = 2;
+let z = x / y;
+```
+
+**Remainder** [S1]
+The modulus operator (`%`) returns the division remainder. The result of a modulo operation is the remainder of an arithmetic division.
+```javascript
+let x = 5;
+let y = 2;
+let z = x % y;
+```
+
+**Incrementing** [S1]
+The increment operator (`++`) increments numbers.
+```javascript
+let x = 5;
+x++;
+let z = x;
+```
+
+**Decrementing** [S1]
+The decrement operator (`--`) decrements numbers.
+```javascript
+let x = 5;
+x--;
+let z = x;
+```
+
+**Exponentiation** [S1]
+The exponentiation operator (`**`) raises the first operand to the power of the second operand.
+```javascript
+let x = 5;
+let z = x ** 2;
+```
+`x ** y` produces the same result as `Math.pow(x, y)`:
+```javascript
+let x = 5;
+let z = Math.pow(x,2);
+```
+
+**Operator Precedence** [S1]
+Operator precedence describes the order in which operations are performed in an arithmetic expression. Multiplication and division have higher precedence than addition and subtraction:
+```javascript
+let x = 100 + 50 * 3;
+```
+Parentheses can change the order — operations inside parentheses are computed first:
+```javascript
+let x = (100 + 50) * 3;
+```
+When many operations have the same precedence (like addition and subtraction or multiplication and division), they are computed from left to right:
+```javascript
+let x = 100 + 50 - 3;
+```
+```javascript
+let x = 100 / 50 * 3;
+```
+
+## 🛠️ 적용 사례 (Applied in summary)
+The page's own snippets are the canonical applied examples — adding/subtracting/multiplying/dividing into `z`, taking a remainder with `%`, incrementing/decrementing, exponentiating with `**` vs `Math.pow`, and demonstrating precedence with and without parentheses. No external project/commit applications found in the source.
+
+## 💻 코드 패턴 (Code patterns)
+Operate over two variables:
+```javascript
+let x = 5;
+let y = 2;
+let z = x % y;
+```
+Exponentiate (two equivalent forms):
+```javascript
+let z = x ** 2;
+let z = Math.pow(x,2);
+```
+Override precedence with parentheses:
+```javascript
+let x = (100 + 50) * 3;
+```
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+No contradictions found in the source. The source notes the exponentiation operator `**` was introduced in ES2016, which is the relevant version context.
+
+## ✅ 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 Operators]], [[JavaScript Assignment]], [[JavaScript Types]], [[JavaScript Comparisons]]
+- **참조 맥락:** Referenced whenever computing numeric values or reasoning about evaluation order in expressions.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — JavaScript Arithmetic — https://www.w3schools.com/js/js_arithmetic.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript Arithmetic" page (Astra wiki-curation, P-Reinforce v3.1 format).