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-object-display
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title: "JavaScript Object Display"
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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: ["JS object display", "object Object", "JSON.stringify", "Object.values", "Object.entries", "for in loop", "display object"]
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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", "objects", "display", "json"]
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raw_sources: ["https://www.w3schools.com/js/js_object_display.asp"]
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applied_in: []
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github_commit: ""
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---
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# [[JavaScript Object Display]]
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## 🎯 한 줄 통찰 (One-line insight)
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Displaying a JavaScript object directly outputs `[object Object]`; to show its data, name the properties, loop over them, or convert the object with `Object.values()`/`Object.entries()`/`JSON.stringify()`. [S1]
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## 🧠 핵심 개념 (Core concepts)
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- **Direct display gives `[object Object]`** — this appears when you insert an object where a string is expected. [S1]
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- **Name the properties** — properties can be concatenated into a string by name. [S1]
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- **Loop with `for...in`** — collect property values in a loop, using `person[x]` (not `person.x`). [S1]
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- **`Object.values()`** — creates an array from the property values. [S1]
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- **`Object.entries()`** — makes it simple to use objects in loops as `[key, value]` pairs. [S1]
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- **`JSON.stringify()`** — converts an object to a JSON-notation string; built in and supported in all browsers. [S1]
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## 🧩 추출된 패턴 (Extracted patterns)
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- **`for...in` with bracket access** — `text += person[x]` works because `x` is the loop variable holding the key. [S1]
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- **Values-to-string** — `Object.values(person).toString()` flattens values into a comma-joined string. [S1]
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- **Destructured entries loop** — `for (let [fruit, value] of Object.entries(fruits))` iterates key/value pairs. [S1]
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## 📖 세부 내용 (Details)
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**How to Display JavaScript Objects?**
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Displaying a JavaScript object will output `[object Object]`. [S1]
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```javascript
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// Create an Object
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const person = {
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name: "John",
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age: 30,
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city: "New York"
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};
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let text = person;
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```
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**Why do I See [object Object]?**
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`[object Object]` appears when you attempt to insert an object (a data structure containing properties) into a context where a string is expected; it represents how JavaScript handles this situation. Solutions include displaying the object properties by name, in a loop, via `Object.values()`, or via `JSON.stringify()`. [S1]
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**Displaying Object Properties**
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The properties of an object can be added in a string: [S1]
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```javascript
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// Create an Object
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const person = {
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name: "John",
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age: 30,
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city: "New York"
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};
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// Add Properties
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let text = person.name + "," + person.age + "," + person.city;
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```
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**Using a For .. In Loop**
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The properties of an object can be collected in a loop: [S1]
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```javascript
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// Create an Object
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const person = {
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name: "John",
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age: 30,
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city: "New York"
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};
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// Build a Text
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let text = "";
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for (let x in person) {
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text += person[x] + " ";
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};
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```
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You must use `person[x]` in the loop. `person.x` will not work, because `x` is the loop variable. [S1]
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**Using Object.values()**
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`Object.values()` creates an array from the property values: [S1]
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```javascript
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// Create an Object
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const person = {
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name: "John",
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age: 30,
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city: "New York"
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};
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// Create an Array
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const myArray = Object.values(person);
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// Stringify the Array
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let text = myArray.toString();
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```
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**Using Object.entries()**
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`Object.entries()` makes it simple to use objects in loops: [S1]
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```javascript
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const fruits = {Bananas:300, Oranges:200, Apples:500};
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let text = "";
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for (let [fruit, value] of Object.entries(fruits)) {
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text += fruit + ": " + value + "<br>";
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}
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```
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**Using JSON.stringify()**
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JavaScript objects can be converted to a string with the JSON method `JSON.stringify()`. `JSON.stringify()` is included in JavaScript and supported in all browsers. The result is a string written in JSON notation: [S1]
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```javascript
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{"name":"John","age":50,"city":"New York"}
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```
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```javascript
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// Create an Object
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const person = {
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name: "John",
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age: 30,
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city: "New York"
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};
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// Stringify Object
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let text = JSON.stringify(person);
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```
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## ⚖️ 비교 및 선택 기준 (Comparison & decision criteria)
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| Technique | Output shape | Use when |
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| --- | --- | --- |
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| Property by name | Hand-built string | You know the exact properties [S1] |
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| `for...in` loop | Concatenated values | Iterate all properties generically [S1] |
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| `Object.values()` | Array of values | You only need the values [S1] |
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| `Object.entries()` | `[key, value]` pairs | You need both keys and values in a loop [S1] |
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| `JSON.stringify()` | JSON-notation string | Serialize the whole object [S1] |
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## 🛠️ 적용 사례 (Applied in summary)
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The page's own snippets are the canonical applied examples — the `[object Object]` pitfall, property-by-name concatenation, the `for...in` loop, `Object.values().toString()`, the `Object.entries()` destructured loop, and `JSON.stringify(person)`. No external project/commit applications found in the source.
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## 💻 코드 패턴 (Code patterns)
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For...in loop (note bracket access):
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```javascript
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let text = "";
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for (let x in person) {
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text += person[x] + " ";
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};
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```
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Entries loop with destructuring:
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```javascript
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for (let [fruit, value] of Object.entries(fruits)) {
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text += fruit + ": " + value + "<br>";
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}
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```
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Serialize to JSON:
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```javascript
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let text = JSON.stringify(person);
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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 Objects]], [[JavaScript Object Properties]], [[JavaScript Object Methods]]
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- **참조 맥락:** Referenced whenever rendering object data to the page or serializing it for transport.
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## 📚 출처 (Sources)
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- [S1] W3Schools — JavaScript Object Display — https://www.w3schools.com/js/js_object_display.asp
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## 📝 변경 이력 (Change history)
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- 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript Object Display" page (Astra wiki-curation, P-Reinforce v3.1 format).
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