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-class-inheritance
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title: "JavaScript Class Inheritance"
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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: ["extends", "super", "getters and setters", "class hoisting", "subclass"]
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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", "classes", "inheritance", "oop"]
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raw_sources: ["https://www.w3schools.com/js/js_class_inheritance.asp"]
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applied_in: []
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github_commit: ""
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---
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# [[JavaScript Class Inheritance]]
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## 🎯 한 줄 통찰 (One-line insight)
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Use `extends` to make one class inherit all methods of another and `super()` to reach the parent's constructor; classes also support `get`/`set` accessors and, unlike functions, are not hoisted. [S1]
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## 🧠 핵심 개념 (Core concepts)
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- **`extends` for inheritance** — a class created with `extends` acquires all methods from another class. [S1]
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- **`super()` references the parent** — calling `super()` in the constructor accesses parent properties and methods. [S1]
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- **Inheritance aids reuse** — inheritance is useful for code reusability. [S1]
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- **Getters and setters** — classes support `get` and `set` keywords for special property handling. [S1]
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- **Getter access has no parentheses** — even though the getter is a method, you do not use parentheses to get the property value. [S1]
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- **Classes are not hoisted** — unlike functions, classes must be declared before use. [S1]
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## 🧩 추출된 패턴 (Extracted patterns)
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- **Subclass = `extends` + `super(...)`** — pass parent constructor arguments through `super()`, then add subclass-specific state. [S1]
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- **Underscore backing field for accessors** — store the value in `_carname` and expose it via `get carname()` / `set carname(x)` to avoid name collision with the accessor. [S1]
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- **Declare before use** — because classes aren't hoisted, place the declaration ahead of any `new`. [S1]
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## 📖 세부 내용 (Details)
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**Class Inheritance**
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To create class inheritance, use the `extends` keyword; the subclass acquires all methods of the parent. `super()` refers to the parent class, and calling it in the constructor accesses parent properties and methods. Inheritance is useful for code reusability: [S1]
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```javascript
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class Car {
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constructor(brand) {
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this.carname = brand;
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}
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present() {
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return 'I have a ' + this.carname;
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}
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}
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class Model extends Car {
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constructor(brand, mod) {
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super(brand);
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this.model = mod;
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}
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show() {
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return this.present() + ', it is a ' + this.model;
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}
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}
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let myCar = new Model("Ford", "Mustang");
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document.getElementById("demo").innerHTML = myCar.show();
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```
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**Getters and Setters**
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Classes support getters and setters using the `get` and `set` keywords: [S1]
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```javascript
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class Car {
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constructor(brand) {
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this.carname = brand;
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}
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get cnam() {
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return this.carname;
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}
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set cnam(x) {
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this.carname = x;
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}
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}
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const myCar = new Car("Ford");
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document.getElementById("demo").innerHTML = myCar.cnam;
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```
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**Note:** Even if the getter is a method, you do not use parentheses when you want to get the property value. [S1]
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Using an underscore backing field so the accessor name matches the property: [S1]
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```javascript
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class Car {
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constructor(brand) {
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this._carname = brand;
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}
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get carname() {
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return this._carname;
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}
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set carname(x) {
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this._carname = x;
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}
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}
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const myCar = new Car("Ford");
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document.getElementById("demo").innerHTML = myCar.carname;
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```
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Using the setter to change the value: [S1]
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```javascript
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class Car {
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constructor(brand) {
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this._carname = brand;
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}
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get carname() {
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return this._carname;
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}
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set carname(x) {
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this._carname = x;
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}
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}
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const myCar = new Car("Ford");
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myCar.carname = "Volvo";
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document.getElementById("demo").innerHTML = myCar.carname;
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```
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**Hoisting**
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Class declarations are not hoisted; classes must be declared before use: [S1]
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```javascript
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//You cannot use the class yet.
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//myCar = new Car("Ford") will raise an error.
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class Car {
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constructor(brand) {
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this.carname = brand;
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}
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}
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//Now you can use the class:
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const myCar = new Car("Ford")
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```
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For other declarations, like functions, you will NOT get an error when you try to use it before it is declared, because the default behavior of JavaScript declarations is hoisting. [S1]
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## 🛠️ 적용 사례 (Applied in summary)
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The `Car` / `Model` pair is the running applied example for `extends` and `super()`; the `_carname` accessor examples demonstrate getters/setters, and the hoisting snippet shows the declare-before-use requirement. No external project/commit applications found in the source.
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## 💻 코드 패턴 (Code patterns)
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Subclass with `extends` and `super()` (language: JavaScript):
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```javascript
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class Model extends Car {
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constructor(brand, mod) {
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super(brand);
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this.model = mod;
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}
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show() {
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return this.present() + ', it is a ' + this.model;
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}
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}
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```
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Getter/setter with an underscore backing field:
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```javascript
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get carname() { return this._carname; }
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set carname(x) { this._carname = x; }
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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 Classes]], [[JavaScript Class Static]], [[JavaScript Objects]], [[JavaScript Object Accessors]]
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- **참조 맥락:** Builds on JavaScript Classes by adding inheritance (`extends`/`super`), accessors, and hoisting behavior.
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## 📚 출처 (Sources)
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- [S1] W3Schools — JavaScript Class Inheritance — https://www.w3schools.com/js/js_class_inheritance.asp
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## 📝 변경 이력 (Change history)
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- 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript Class Inheritance" page (Astra wiki-curation, P-Reinforce v3.1 format).
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