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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>
182 lines
6.7 KiB
Markdown
182 lines
6.7 KiB
Markdown
---
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id: javascript-output
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title: "JavaScript Output"
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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: ["innerHTML", "document.write", "window.alert", "console.log", "JS display data"]
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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", "output", "innerhtml", "console-log"]
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raw_sources: ["https://www.w3schools.com/js/js_output.asp"]
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applied_in: []
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github_commit: ""
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---
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# [[JavaScript Output]]
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## 🎯 한 줄 통찰 (One-line insight)
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JavaScript can display data four ways — writing into an HTML element (`innerHTML`/`innerText`), HTML output via `document.write()`, an alert box via `window.alert()`, and the browser console via `console.log()`. [S1]
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## 🧠 핵심 개념 (Core concepts)
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- **Four display possibilities** — `innerHTML`/`innerText` (into an HTML element), `document.write()` (HTML output), `window.alert()` (alert box), `console.log()` (browser console). [S1]
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- **`innerHTML` is the most common** — accessing an element with `document.getElementById(id)` and setting `innerHTML` is the most common way to display data in HTML. [S1]
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- **`innerHTML` vs `innerText`** — use `innerHTML` when you want to change an HTML element; use `innerText` when you only want to change the plain text. [S1]
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- **`document.write()` is for testing only** — using it after the document has loaded will delete all existing HTML. [S1]
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- **`console.log()` is for debugging.** [S1]
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- **No print object** — JavaScript has no print object/method; the only exception is `window.print()` to print the current window. [S1]
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## 🧩 추출된 패턴 (Extracted patterns)
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- **Select-then-write pattern** — `document.getElementById("demo").innerHTML = ...` is the standard way to inject results into the page. [S1]
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- **Testing vs production output** — `document.write()` and `alert()` are quick test outputs; `console.log()` is the debugging channel; `innerHTML`/`innerText` are the production display. [S1]
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- **Optional `window` prefix** — `window.alert()` and `alert()` are equivalent because `window` is the global scope object. [S1]
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## 📖 세부 내용 (Details)
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**JavaScript Display Possibilities** — JavaScript can "display" data in four ways: writing into an HTML element using `innerHTML` or `innerText`, writing into the HTML output using `document.write()`, writing into an alert box using `window.alert()`, and writing into the browser console using `console.log()`. [S1]
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**Using innerHTML** — To access an HTML element, use the `document.getElementById(id)` method, then use the `innerHTML` property to change the HTML content. Changing the `innerHTML` property is the most common way to display data in HTML. [S1]
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```html
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<!DOCTYPE html>
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<html>
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<body>
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<h1>My First Web Page</h1>
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<p>My First Paragraph</p>
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<p id="demo"></p>
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<script>
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document.getElementById("demo").innerHTML = "<h2>Hello World</h2>";
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</script>
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</body>
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</html>
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```
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**Using innerText** — Use the `innerText` property to change the plain text content of an HTML element. Use `innerHTML` when you want to change an HTML element; use `innerText` when you only want to change the plain text. [S1]
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```html
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<!DOCTYPE html>
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<html>
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<body>
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<h1>My First Web Page</h1>
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<p>My First Paragraph</p>
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<p id="demo"></p>
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<script>
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document.getElementById("demo").innerText = "Hello World";
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</script>
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</body>
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</html>
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```
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**Using document.write()** — For testing purposes, it is convenient to use `document.write()`. Using `document.write()` after an HTML document is loaded will delete all existing HTML; the method should only be used for testing. [S1]
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```html
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<!DOCTYPE html>
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<html>
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<body>
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<h1>My First Web Page</h1>
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<p>My first paragraph.</p>
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<script>
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document.write(5 + 6);
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</script>
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</body>
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</html>
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```
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```html
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<!DOCTYPE html>
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<html>
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<body>
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<h1>My First Web Page</h1>
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<p>My first paragraph.</p>
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<button type="button" onclick="document.write(5 + 6)">Try it</button>
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</body>
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</html>
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```
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**Using window.alert()** — You can use an alert box to display data. The `window` keyword is optional because `window` is the global scope object. [S1]
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```html
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<!DOCTYPE html>
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<html>
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<body>
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<h1>My First Web Page</h1>
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<p>My first paragraph.</p>
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<script>
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window.alert(5 + 6);
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</script>
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</body>
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</html>
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```
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```html
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<!DOCTYPE html>
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<html>
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<body>
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<h1>My First Web Page</h1>
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<p>My first paragraph.</p>
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<script>
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alert(5 + 6);
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</script>
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</body>
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</html>
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```
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**Using console.log()** — For debugging purposes, you can use the `console.log()` method to display data in the browser console. [S1]
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```html
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<!DOCTYPE html>
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<html>
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<body>
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<script>
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console.log(5 + 6);
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</script>
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</body>
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</html>
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```
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**JavaScript Print** — JavaScript does not have any print object or print methods. You cannot access output devices from JavaScript. The only exception is that you can call the `window.print()` method in the browser to print the content of the current window. [S1]
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```html
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<!DOCTYPE html>
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<html>
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<body>
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<button onclick="window.print()">Print this page</button>
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</body>
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</html>
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```
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## 🛠️ 적용 사례 (Applied in summary)
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The page's own snippets are the canonical applied examples — injecting markup with `innerHTML`, plain text with `innerText`, test output with `document.write()`/`alert()`, debug output with `console.log()`, and `window.print()` on a button. No external project/commit applications found in the source.
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## 💻 코드 패턴 (Code patterns)
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Display into an element:
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```javascript
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document.getElementById("demo").innerHTML = "<h2>Hello World</h2>";
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```
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Debug to console:
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```javascript
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console.log(5 + 6);
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```
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Alert box:
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```javascript
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window.alert(5 + 6);
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```
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## ⚖️ 모순 및 업데이트 (Contradictions & updates)
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No contradictions found in the source. (The source itself cautions that `document.write()` after load deletes existing HTML — a caveat, not a contradiction.)
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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 Introduction]], [[JavaScript Where To]], [[JavaScript Statements]]
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- **참조 맥락:** Referenced whenever results need to be shown to a user or developer.
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## 📚 출처 (Sources)
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- [S1] W3Schools — JavaScript Output — https://www.w3schools.com/js/js_output.asp
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## 📝 변경 이력 (Change history)
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- 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript Output" page (Astra wiki-curation, P-Reinforce v3.1 format).
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