2nd/10_Wiki/Topics/Domain_Programming/Topic_JavaScript/JavaScript_Assignment.md

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id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
javascript-assignment	JavaScript Assignment	Frontend	draft	conceptual		JS assignment operators compound assignment logical assignment falsy values truthy values nullish coalescing assignment spread operator		B	0.87	2026-06-23	2026-06-23			javascript js web frontend w3schools assignment operators	https://www.w3schools.com/js/js_assignment.asp

JavaScript Assignment

🎯 한 줄 통찰 (One-line insight)

Assignment operators assign values to variables — = for a plain assignment and compound forms (+=, -=, *=, **=, /=, %=) plus logical forms (&&=, ||=, ??=) for assign-and-operate in one step. [S1]

🧠 핵심 개념 (Core concepts)

• Assignment operators assign values — they assign values to JavaScript variables. [S1]
• Compound assignment — arithmetic compound operators combine an operation with assignment, e.g. x += y is the same as x = x + y. [S1]
• Logical assignment — &&=, ||=, and ??= assign conditionally based on truthiness/falsiness/nullishness. [S1]
• 8 falsy values — false, 0, -0, 0n, "" (empty strings), null, undefined, and NaN are falsy. [S1]
• Truthy surprises — "0", "false", [], and {} are truthy even though they look "empty". [S1]
• Spread ... — the ... operator splits iterables into individual elements. [S1]

🧩 추출된 패턴 (Extracted patterns)

• Mutate in place — apply an operation to a variable and store back with one compound operator (x += 5). [S1]
• Conditional assignment — x ??= 10 assigns only when x is null/undefined; x ||= 10 when falsy; x &&= 10 when truthy. [S1]
• Falsy check awareness — remember "0" and "false" strings (and []/{}) are truthy when writing conditions. [S1]

📖 세부 내용 (Details)

JavaScript Assignment Operators [S1] Assignment operators assign values to JavaScript variables. Using x = 10 and y = 5 for the examples below, the result column shows the value after applying the operator:

Operator	Example	Same As	Result
=	x = y	x = y	x = 5
+=	x += y	x = x + y	x = 15
-=	x -= y	x = x - y	x = 5
*=	x *= y	x = x * y	x = 50
**=	x **= y	x = x ** y	x = 100000
/=	x /= y	x = x / y	x = 2
%=	x %= y	x = x % y	x = 0

The = Operator [S1]

let x = 10;

The += Operator [S1]

let x = 10;
x += 5;

The -= Operator [S1]

let x = 10;
x -= 5;

*The = Operator [S1]

let x = 10;
x *= 5;

**The = Operator [S1]

let x = 10;
x **= 5;

The /= Operator [S1]

let x = 10;
x /= 5;

The %= Operator [S1]

let x = 10;
x %= 5;

Logical Assignment Operators [S1]

The &&= Operator (Logical AND assignment):

let x = true;
let y = x &&= 10;

The ||= Operator (Logical OR assignment):

let x = false;
let y = x ||= 10;

The ??= Operator (Nullish Coalescing assignment):

let x;
x ??= 10;

The 8 FALSY Values [S1] The following values are falsy: false, 0, -0, 0n, "" / '' / `` (empty strings), null, undefined, and NaN.

These are TRUTHY [S1] The following values are truthy: "0" (string), "false" (string), [] (empty array), and {} (empty object).

The Spread (...) Operator [S1] The ... operator splits iterables into individual elements.

🛠️ 적용 사례 (Applied in summary)

The page's own snippets are the canonical applied examples — each compound operator demonstrated against let x = 10, and the logical-assignment operators shown against boolean/undefined seeds. No external project/commit applications found in the source.

💻 코드 패턴 (Code patterns)

Compound arithmetic assignment:

let x = 10;
x += 5;

Nullish-coalescing assignment (only assigns when null/undefined):

let x;
x ??= 10;

Logical OR assignment (assigns when falsy):

let x = false;
let y = x ||= 10;

⚖️ 모순 및 업데이트 (Contradictions & updates)

No contradictions found in the source. Worth noting: "0", "false", [], and {} are truthy despite intuition, which the source explicitly flags.

✅ 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: 0.87
• 중복 검사 결과: 신규 생성 (New discovery)

🔗 지식 그래프 (Knowledge Graph)

• 상위/루트: JavaScript Tutorial
• 관련 개념: JavaScript Operators, JavaScript Arithmetic, JavaScript Comparisons, JavaScript Types
• 참조 맥락: Referenced whenever updating a variable's value or doing conditional/defaulting assignment.

📚 출처 (Sources)

• [S1] W3Schools — JavaScript Assignment — https://www.w3schools.com/js/js_assignment.asp

📝 변경 이력 (Change history)

• 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript Assignment" page (Astra wiki-curation, P-Reinforce v3.1 format).