2nd/10_Wiki/Topic_JavaScript/JavaScript_Function_Intro.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-function-definitions	JavaScript Function Definitions	Frontend	draft	conceptual		function definitions function declaration function syntax defining functions local variables function intro		B	0.86	2026-06-23	2026-06-23			javascript js web frontend w3schools functions definitions	https://www.w3schools.com/js/js_function_intro.asp

JavaScript Function Definitions

🎯 한 줄 통찰 (One-line insight)

A function is defined with the function keyword, a name, a parenthesized parameter list, and a body — once defined it is a reusable block that runs only when called. [S1]

🧠 핵심 개념 (Core concepts)

• Functions are code blocks — reusable code designed to perform a particular task; they execute when called or invoked. [S1]
• Definition syntax — function name(p1, p2, ...) { ... }: keyword, name, comma-separated parameters in parentheses, body in braces. [S1]
• Why define functions — to reuse code (write once, run many times) and organize code into manageable sections. [S1]
• Run on call — the body does not run at definition time; it runs when the function is invoked. [S1]
• Local variables — variables declared inside a function are accessible only within it, created when the function starts and deleted when it completes. [S1]
• Functions as variable values — a function call can be used wherever a value is expected. [S1]

🧩 추출된 패턴 (Extracted patterns)

• Name → parameters → body — the standard declaration shape that makes a block callable by name. [S1]
• Parameterized reuse — define once with parameters, call repeatedly with different arguments. [S1]
• Scope by definition — placing a let inside the function body confines it to that function. [S1]

📖 세부 내용 (Details)

Functions are Code Blocks — functions are reusable code blocks designed to perform a particular task; they execute when they are called or invoked. [S1]

Why Use Functions? — functions let you reuse code (write once, run many times) and organize code into manageable sections. [S1]

JavaScript Function Syntax — a function is defined with the function keyword, a name, parameters in parentheses, and a body in curly braces: [S1]

function name( p1, p2, ... ) {
  // code to be executed
}

What Does a Function Look Like? — a basic definition: [S1]

function sayHello() {
  return "Hello World";
}

Functions Run When You Call Them — the defined function runs only when invoked, and the returned value can be stored: [S1]

function sayHello() {
  return "Hello World";
}

let message = sayHello();

A definition with parameters: [S1]

function multiply(a, b) {
  return a * b;
}

A Function Can Be Used Many Times — the same definition is reused with different arguments: [S1]

function add(a, b) {
  return a + b;
}

let sum1 = add(5, 5);
let sum2 = add(50, 50);

Local Variables — variables declared inside a function can only be accessed from within the function; they are created when the function starts and deleted when it completes: [S1]

// code here can NOT use carName

function myFunction() {
  let carName = "Volvo";
  // code here CAN use carName
}

// code here can NOT use carName

Functions Used as Variables — a function call can be used directly inside an expression: [S1]

let x = toCelsius(77);
let text = "The temperature is " + x + " Celsius";

And inlined directly: [S1]

let text = "The temperature is " + toCelsius(77) + " Celsius";

🛠️ 적용 사례 (Applied in summary)

The page's own snippets are the canonical applied examples — defining sayHello(), multiply(a, b), the reusable add(a, b), the scoped myFunction(), and using toCelsius(77) as a value. No external project/commit applications found in the source.

💻 코드 패턴 (Code patterns)

Define a function (language: JavaScript):

function name( p1, p2, ... ) {
  // code to be executed
}

Define and reuse with parameters:

function add(a, b) {
  return a + b;
}

let sum1 = add(5, 5);
let sum2 = add(50, 50);

Confine a variable to a function:

function myFunction() {
  let carName = "Volvo";
}

⚖️ 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: 0.86
• 중복 검사 결과: 신규 생성 (New discovery)

🔗 지식 그래프 (Knowledge Graph)

• 상위/루트: JavaScript Tutorial
• 관련 개념: JavaScript Functions, JavaScript Function Invocation, JavaScript Function Parameters, JavaScript Function Returns
• 참조 맥락: Referenced when learning how to declare and scope a reusable callable block.

📚 출처 (Sources)

• [S1] W3Schools — JavaScript Function Definitions — https://www.w3schools.com/js/js_function_intro.asp

📝 변경 이력 (Change history)

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