---
id: json-data-types
title: "JSON Data Types"
category: "Frontend"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["JSON data types", "JSON values", "JSON valid types", "JSON string number boolean null", "JSON type rules"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.9
created_at: 2026-06-23
updated_at: 2026-06-23
review_reason: ""
merge_history: []
tags: ["javascript", "js", "web", "frontend", "w3schools", "json", "data-types"]
raw_sources: ["https://www.w3schools.com/js/js_json_datatypes.asp"]
applied_in: []
github_commit: ""
---

# [[JSON Data Types]]

## 🎯 한 줄 통찰 (One-line insight)
A JSON value must be one of exactly six data types — string, number, object, array, boolean, or null — and cannot be a function, a date, or undefined. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Six valid value types** — a string, a number, an object (JSON object), an array, a boolean, or null. [S1]
- **Three invalid value types** — JSON values cannot be a function, a date, or undefined. [S1]
- **Strings need double quotes** — strings in JSON must be written in double quotes. [S1]
- **Numbers are integer or float** — numbers in JSON must be an integer or a floating point. [S1]
- **Nested objects must follow JSON syntax** — objects used as values must themselves be valid JSON. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Type-per-value pattern** — each value in a name/value pair is constrained to the six legal types. [S1]
- **Double-quoted strings** — `{"name":"John"}`. [S1]
- **Composite values** — values may themselves be objects or arrays, enabling nesting. [S1]

## 📖 세부 내용 (Details)
**Valid data types**
In JSON, values must be one of the following data types: a string, a number, an object (JSON object), an array, a boolean, or null. JSON values cannot be one of the following data types: a function, a date, or undefined. [S1]

**JSON strings**
Strings in JSON must be written in double quotes. [S1]
```json
{"name":"John"}
```

**JSON numbers**
Numbers in JSON must be an integer or a floating point. [S1]
```json
{"age":30}
```

**JSON objects**
Values in JSON can be objects. [S1]
```json
{
"employee":{"name":"John", "age":30, "city":"New York"}
}
```
Objects as values in JSON must follow the JSON syntax. [S1]

**JSON arrays**
Values in JSON can be arrays. [S1]
```json
{
"employees":["John", "Anna", "Peter"]
}
```

**JSON booleans**
Values in JSON can be true/false. [S1]
```json
{"sale":true}
```

**JSON null**
Values in JSON can be null. [S1]
```json
{"middlename":null}
```

## 🛠️ 적용 사례 (Applied in summary)
The page's snippets each demonstrate one legal value type in a name/value pair (string, number, nested object, array, boolean, null). No external project/commit applications found in the source.

## 💻 코드 패턴 (Code patterns)
One name/value pair per legal type:
```json
{"name":"John"}
{"age":30}
{"employee":{"name":"John", "age":30, "city":"New York"}}
{"employees":["John", "Anna", "Peter"]}
{"sale":true}
{"middlename":null}
```

## ⚖️ 비교 및 선택 기준 (Comparison & decision criteria)
What JSON allows vs forbids as a value: [S1]
- **Allowed** — string, number (integer or floating point), object, array, boolean, null.
- **Forbidden** — function, date, undefined.
- **Implication** — to carry a date or function in JSON you must encode it as a string and reconstruct it at the receiver (handled on the Parse/Stringify pages).

## ⚖️ 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:** 0.90
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[JavaScript Tutorial]]
- **관련 개념:** [[JavaScript JSON Syntax]], [[JavaScript JSON Objects]], [[JavaScript JSON Arrays]], [[JavaScript JSON Stringify]]
- **참조 맥락:** Referenced when validating that a value is legal JSON before serializing or transmitting.

## 📚 출처 (Sources)
- [S1] W3Schools — JSON Data Types — https://www.w3schools.com/js/js_json_datatypes.asp

## 📝 변경 이력 (Change history)
- 2026-06-23: Initial draft synthesized from the W3Schools "JSON Data Types" page (Astra wiki-curation, P-Reinforce v3.1 format).
