refactor(topics): 멀티 에이전트용 지식 재편 — _Common(공통 기본기) + Domain_* 구조
에이전트 8종(대화형/프로그래머 C·S/디자이너/설계자/기획자/QA/PD/PM)에게 [공통 기본 능력 + 롤별 Specialty] 2층으로 지식을 주입하기 위한 재분류. 문서 내용·포맷은 무수정, 폴더 이동만 (6,372개 문서 수 보존 확인). - Topic_Programming → Domain_Programming (내부 구조 보존) - Topic_Graphic → Domain_Design - Topic_Business → Domain_Product - Topic_General → Domain_General - _Common 신설: Math(구 Topic_Math_Specialty), Reasoning(구 General/From_Thinking & Reasoning), Reasoning_Creativity(구 General/From_창의성), Communication(Poetic_Blog_Writing + From_writing) - 타 도메인의 From_* 폴더는 유지 (출처 표기일 뿐, 이미 도메인에 맞게 분류된 문서) - 빈 폴더 정리 (memory/procedures) - 에이전트→폴더 매핑은 workspace의 .astra/agent-knowledge-map.json (9개 에이전트) Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Antigravity Agent
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---
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id: javascript-booleans
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title: "JavaScript Booleans"
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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: ["boolean", "true false", "JS booleans", "Boolean function", "truthy falsy"]
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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", "boolean", "truthy", "data-types"]
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raw_sources: ["https://www.w3schools.com/js/js_booleans.asp"]
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applied_in: []
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github_commit: ""
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---
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# [[JavaScript Booleans]]
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## 🎯 한 줄 통찰 (One-line insight)
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A Boolean is a primitive type with only two values — `true` or `false` — and the boolean value of an expression is the basis for all JavaScript comparisons and conditions. [S1]
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## 🧠 핵심 개념 (Core concepts)
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- **Two values only** — a Boolean can only have one of two values: `true` or `false`, written in lowercase and without quotes. [S1]
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- **Comparisons return booleans** — all JavaScript comparison operators (`==`, `!=`, `<`, `>`) return `true` or `false`. [S1]
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- **Drives control flow** — booleans are used in `if` statements and loops to decide which code blocks run. [S1]
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- **`Boolean()` evaluates truthiness** — the `Boolean()` function reports whether an expression or variable is true. [S1]
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- **Truthy vs falsy** — everything with a "value" is true; everything without a "value" is false. [S1]
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- **Avoid Boolean objects** — booleans can be created as objects with `new Boolean()`, but this should not be done. [S1]
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## 🧩 추출된 패턴 (Extracted patterns)
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- **Coerce-to-boolean check** — wrap an expression in `Boolean(...)` (or rely on an expression like `(10 > 9)`) to obtain its truth value. [S1]
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- **Truthiness rule** — empty arrays `[]` and empty objects `{}` are truthy because all objects evaluate to true; `0`, `""`, `undefined`, `null`, `NaN`, and `false` are falsy. [S1]
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- **Never compare a primitive boolean to a Boolean object** — `(x == y)` may be true while `(x === y)` is false, and two objects always compare as not equal. [S1]
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## 📖 세부 내용 (Details)
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**The Boolean data type** [S1]
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In JavaScript, a Boolean is a primitive data type that can only have one of two values: `true` or `false`. The boolean value of an expression is the basis for all JavaScript comparisons and conditions. `true` and `false` are boolean data types, are the only possible boolean values, and must be written in lowercase and without quotes.
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**Boolean use cases** [S1]
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Very often, in programming, you will need a data type that can represent one of two values, like: yes or no; on or off; true or false. Boolean values are fundamental for logical operations and control flow.
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**Comparisons** [S1]
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All JavaScript comparison operators (like `==`, `!=`, `<`, `>`) return `true` or `false`. Given that `x = 5`:
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| Description | Example | Returns |
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|---|---|---|
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| Equal to | (x == 8) | false |
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| Not equal to | (x != 8) | true |
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| Greater than | (x > 8) | false |
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| Less than | (x < 8) | true |
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```javascript
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let x = 5;
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(x == 8); // equals false
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(x != 8); // equals true
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```
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**Conditions** [S1]
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Booleans are extensively used in `if` statements to determine which code blocks to execute.
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| Example | Result |
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|---|---|
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| if (day == "Monday") | true or false |
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| if (salary > 9000) | true or false |
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| if (age < 18) | true or false |
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```javascript
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if (hour < 18) {
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greeting = "Good day";
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} else {
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greeting = "Good evening";
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}
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```
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**Loops** [S1]
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Booleans are extensively used in loops to determine the looping condition.
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| Description | Example |
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|---|---|
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| For loop | for (i = 0; i < 5; i++) |
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| While loop | while (i < 10) |
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| For in loop | for (x in person) |
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| For of loop | for (x of cars) |
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```javascript
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while (i < 10) {
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text += i;
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i++;
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}
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```
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**The `Boolean()` function** [S1]
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You can use the `Boolean()` function to find out if an expression (or a variable) is true:
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```javascript
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Boolean(10 > 9)
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```
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Or even easier:
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```javascript
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(10 > 9)
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```
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**Everything with a "value" is true** [S1]
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The following all evaluate to true: `100`, `3.14`, `-15`, `true`, `"Hello"`, `"false"`, `(7 + 1 + 3.14)`, `[ ]`, `{ }`.
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Note: In JavaScript, both an empty array `[ ]` and an empty object `{ }` are truthy because they are objects. All objects in JavaScript evaluate to true in a boolean context, regardless of their content.
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**Everything without a "value" is false** [S1]
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The following all evaluate to false: `0`, `""`, `undefined`, `null`, `NaN`, `false`.
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The boolean value of `0` (zero) is false:
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```javascript
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let x = 0;
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Boolean(x);
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```
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The boolean value of `-0` (minus zero) is false:
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```javascript
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let x = -0;
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Boolean(x);
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```
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The boolean value of `""` (empty string) is false:
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```javascript
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let x = "";
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Boolean(x);
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```
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The boolean value of `undefined` is false:
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```javascript
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let x;
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Boolean(x);
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```
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The boolean value of `null` is false:
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```javascript
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let x = null;
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Boolean(x);
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```
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The boolean value of `false` is false:
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```javascript
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let x = false;
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Boolean(x);
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```
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The boolean value of `NaN` is false:
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```javascript
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let x = 10 / "Hallo";
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Boolean(x);
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```
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**JavaScript booleans as objects** [S1]
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Normally JavaScript booleans are primitive values created from literals:
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```javascript
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let x = false;
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```
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But booleans can also be defined as objects with the keyword `new`:
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```javascript
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let y = new Boolean(false);
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```
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```javascript
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let x = false;
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let y = new Boolean(false);
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// typeof x returns boolean
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// typeof y returns object
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```
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Warning: Do not create Boolean objects. The `new` keyword complicates the code and slows down execution speed. Boolean objects can produce unexpected results.
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Booleans and boolean objects cannot be safely compared:
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```javascript
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let x = Boolean(false);
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let y = new Boolean(false);
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// (x == y) returns true
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// (x === y) returns false
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```
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Comparing two JavaScript objects always returns false.
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## 🛠️ 적용 사례 (Applied in summary)
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The page's own snippets are the canonical applied examples — comparison results, an `if/else` greeting, a `while` accumulation loop, and `Boolean()` truthiness checks across falsy values. No external project/commit applications found in the source.
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## 💻 코드 패턴 (Code patterns)
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Check truthiness of an expression:
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```javascript
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Boolean(10 > 9)
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```
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Detect a falsy value:
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```javascript
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let x = "";
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Boolean(x); // false
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```
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Avoid Boolean objects (anti-pattern noted by source):
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```javascript
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let y = new Boolean(false); // typeof y returns object
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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 explicitly warns against the `new Boolean()` object form as an anti-pattern.
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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 Comparisons]], [[JavaScript If Else]], [[JavaScript Logical]], [[JavaScript Data Types]]
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- **참조 맥락:** Underlies every condition and comparison; central to truthy/falsy reasoning in conditionals and loops.
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## 📚 출처 (Sources)
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- [S1] W3Schools — JavaScript Booleans — https://www.w3schools.com/js/js_booleans.asp
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## 📝 변경 이력 (Change history)
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- 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript Booleans" page (Astra wiki-curation, P-Reinforce v3.1 format).
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