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>
2026-06-23 19:21:18 +09:00
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+---
+id: javascript-introduction
+title: "JavaScript Introduction"
+category: "Frontend"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["JavaScript", "JS", "JS intro", "ECMAScript", "client-side scripting"]
+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"]
+raw_sources: ["https://www.w3schools.com/js/js_intro.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[JavaScript Introduction]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+JavaScript is the programming language of the web — it programs the *behavior* of web pages, able to read and dynamically change both HTML content and CSS styles. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **JavaScript is the programming language of the web** — it lets you calculate, manipulate, and validate data, and update/change both HTML and CSS. [S1]
+- **The three web layers** — HTML defines the content, CSS specifies the layout, and JavaScript programs the behavior. [S1]
+- **The DOM entry point** — JavaScript reaches HTML elements through the document, most commonly with `document.getElementById()`, then reads/writes their content, attributes, and style. [S1]
+- **Quotes are interchangeable** — JavaScript accepts both single `'` and double `"` quotes for strings. [S1]
+- **Standardized** — JavaScript became an ECMA standard in 1997; the official standard is ECMA-262 and the official language name is ECMAScript. [S1]
+
+## 🧩 추출된 패턴 (Extracted patterns)
+- **Select → mutate pattern** — get a reference to an element (`document.getElementById("id")`), then assign to a property (`.innerHTML`, `.style.*`, an attribute) to change the page. [S1]
+- **Style via `.style` object** — CSS properties are set in JS using camelCase property names on `element.style` (e.g. `fontSize`, not `font-size`). [S1]
+- **Show/hide via display** — toggling `style.display` between `"none"` and `"block"` hides or reveals an element. [S1]
+
+## 📖 세부 내용 (Details)
+**What is JavaScript?**
+JavaScript is the programming language of the web. It can calculate, manipulate, and validate data, and it can update and change both HTML and CSS. [S1]
+
+**JavaScript, HTML and CSS**
+The three layers of standard web technology: HTML to define the content of web pages, CSS to specify the layout of web pages, and JavaScript to program the behavior of web pages. [S1]
+
+**JavaScript Can Change HTML Content**
+One of many JavaScript HTML methods is `getElementById()`. It finds an HTML element (by id) and changes the element content (`innerHTML`): [S1]
+```javascript
+document.getElementById("demo").innerHTML = "Hello JavaScript";
+```
+JavaScript accepts both double and single quotes:
+```javascript
+document.getElementById('demo').innerHTML = 'Hello JavaScript';
+```
+
+**JavaScript Can Change HTML Attribute Values**
+JavaScript can change attribute values dynamically — for example, changing the `src` (source) attribute of an `<img>` tag in response to user interaction (e.g. a light bulb turning on/off). [S1]
+
+**JavaScript Can Change HTML Styles (CSS)**
+Changing the style of an HTML element is a variant of changing an HTML attribute: [S1]
+```javascript
+document.getElementById("demo").style.fontSize = "35px";
+```
+
+**JavaScript Can Hide HTML Elements**
+Hiding HTML elements can be done by changing the `display` style: [S1]
+```javascript
+document.getElementById("demo").style.display = "none";
+```
+
+**JavaScript Can Show HTML Elements**
+Showing hidden HTML elements can also be done by changing the `display` style: [S1]
+```javascript
+document.getElementById("demo").style.display = "block";
+```
+
+**Why study JavaScript?**
+JavaScript is one of the three languages all web developers must learn, alongside HTML and CSS. [S1]
+
+**History**
+JavaScript was invented by Brendan Eich in 1995 and became an ECMA standard in 1997. [S1]
+
+## 🛠️ 적용 사례 (Applied in summary)
+The page's own snippets are the canonical applied examples — selecting `#demo` and mutating its `innerHTML`, `style.fontSize`, and `style.display`. No external project/commit applications found in the source.
+
+## 💻 코드 패턴 (Code patterns)
+Select an element and change its content (language: JavaScript):
+```javascript
+document.getElementById("demo").innerHTML = "Hello JavaScript";
+```
+Change a style:
+```javascript
+document.getElementById("demo").style.fontSize = "35px";
+```
+Hide / show:
+```javascript
+document.getElementById("demo").style.display = "none";
+document.getElementById("demo").style.display = "block";
+```
+
+## ⚖️ 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:** 0.89
+- **중복 검사 결과:** 신규 생성 (New discovery)
+
+## 🔗 지식 그래프 (Knowledge Graph)
+- **상위/루트:** [[JavaScript Tutorial]]
+- **관련 개념:** [[JavaScript Where To]], [[JavaScript Output]], [[JavaScript HTML DOM]], [[HTML JavaScript]]
+- **참조 맥락:** The entry point referenced whenever adding interactive behavior to an HTML/CSS page.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — JavaScript Introduction — https://www.w3schools.com/js/js_intro.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript Introduction" page (Astra wiki-curation, P-Reinforce v3.1 format).