2nd/10_Wiki/Topic_JavaScript/JavaScript_Statements.md

---
id: javascript-statements
title: "JavaScript Statements"
category: "Frontend"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["JS statements", "semicolons", "code blocks", "white space", "JS keywords"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.88
created_at: 2026-06-23
updated_at: 2026-06-23
review_reason: ""
merge_history: []
tags: ["javascript", "js", "web", "frontend", "w3schools", "statements", "semicolons"]
raw_sources: ["https://www.w3schools.com/js/js_statements.asp"]
applied_in: []
github_commit: ""
---

# [[JavaScript Statements]]

## 🎯 한 줄 통찰 (One-line insight)
A JavaScript program is a list of statements — composed of values, operators, expressions, keywords, and comments — executed in the order they are written and separated by semicolons. [S1]

## 🧠 핵심 개념 (Core concepts)
- **A program is a list of statements** — a computer program is a list of "instructions" to be "executed" by a computer; in JavaScript these instructions are called statements. [S1]
- **What statements are made of** — values, operators, expressions, keywords, and comments. [S1]
- **Semicolons separate statements** — semicolons separate JavaScript statements; multiple statements on one line are allowed when separated by semicolons. [S1]
- **White space is ignored** — JavaScript ignores multiple spaces; add spaces around operators for readability. [S1]
- **Line breaks** — for best readability, keep lines under 80 characters and break after an operator. [S1]
- **Code blocks** — statements can be grouped together in code blocks inside curly brackets `{ ... }`, typically defining functions. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Declare-then-assign sequence** — declare variables, then assign and compute across ordered statements. [S1]
- **One-line grouping** — multiple statements may be packed on a single line with semicolons (`a = 5; b = 6; c = a + b;`). [S1]
- **Break-after-operator** — when a statement is too long, break the line after an operator. [S1]
- **Block grouping** — wrap related statements in `{ }` to form a function body executed together. [S1]

## 📖 세부 내용 (Details)
**JavaScript Programs** — A computer program is a list of "instructions" to be "executed" by a computer. In a programming language, these programming instructions are called statements. A JavaScript program is a list of programming statements. In HTML, JavaScript programs are executed by the web browser. [S1]

**JavaScript Statements** — JavaScript statements are composed of values, operators, expressions, keywords, and comments. This statement tells the browser to write "Hello Dolly." inside an HTML element with `id="demo"`: [S1]
```javascript
document.getElementById("demo").innerHTML = "Hello Dolly.";
```
Most JavaScript programs contain many JavaScript statements, executed in the same order as they are written: [S1]
```javascript
let x, y, z;    // Statement 1
x = 5;          // Statement 2
y = 6;          // Statement 3
z = x + y;      // Statement 4
```

**Semicolons ;** — Semicolons separate JavaScript statements. Add a semicolon at the end of each executable statement: [S1]
```javascript
let a, b, c;  // Declare 3 variables
a = 5;        // Assign the value 5 to a
b = 6;        // Assign the value 6 to b
c = a + b;    // Assign the sum of a and b to c
```
When separated by semicolons, multiple statements on one line are allowed: [S1]
```javascript
a = 5; b = 6; c = a + b;
```

**JavaScript White Space** — JavaScript ignores multiple spaces. You can add white space to your script to make it more readable. A good practice is to put spaces around operators (`= + - * /`). [S1]

**JavaScript Line Length and Line Breaks** — For best readability, programmers often like to avoid code lines longer than 80 characters. If a JavaScript statement does not fit on one line, the best place to break it is after an operator: [S1]
```javascript
document.getElementById("demo").innerHTML =
"Hello Dolly!";
```

**JavaScript Code Blocks** — JavaScript statements can be grouped together in code blocks, inside curly brackets `{...}`. The purpose of code blocks is to define statements to be executed together. One place you will find statements grouped together in blocks is in JavaScript functions: [S1]
```javascript
function myFunction() {
  document.getElementById("demo1").innerHTML = "Hello Dolly!";
  document.getElementById("demo2").innerHTML = "How are you?";
}
```

**JavaScript Keywords** — JavaScript statements often start with a keyword to identify the JavaScript action to be performed. The following table lists some of the keywords: [S1]

| Keyword | Description |
|---------|-------------|
| var | Declares a variable |
| let | Declares a block variable |
| const | Declares a block constant |
| if | Marks a block of statements to be executed on a condition |
| switch | Marks a block of statements to be executed in different cases |
| for | Marks a block of statements to be executed in a loop |
| function | Declares a function |
| return | Exits a function |
| try | Implements error handling to a block of statements |

JavaScript keywords are reserved words and cannot be used as names for variables. [S1]

## 🛠️ 적용 사례 (Applied in summary)
The page's own snippets are the canonical applied examples — the ordered `let x, y, z` / assign / sum statements, the one-line `a = 5; b = 6; c = a + b;`, the operator line break, and the two-statement function block. No external project/commit applications found in the source.

## 💻 코드 패턴 (Code patterns)
Ordered statements:
```javascript
let x, y, z;
x = 5;
y = 6;
z = x + y;
```
Code block (function):
```javascript
function myFunction() {
  document.getElementById("demo1").innerHTML = "Hello Dolly!";
  document.getElementById("demo2").innerHTML = "How are you?";
}
```

## ⚖️ 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:** 0.88
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[JavaScript Tutorial]]
- **관련 개념:** [[JavaScript Syntax]], [[JavaScript Comments]], [[JavaScript Variables]]
- **참조 맥락:** Defines the unit of execution referenced by every later control-flow and function topic.

## 📚 출처 (Sources)
- [S1] W3Schools — JavaScript Statements — https://www.w3schools.com/js/js_statements.asp

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