2nd/10_Wiki/Topic_JavaScript/JavaScript_Destructuring.md

---
id: javascript-destructuring
title: "JavaScript Destructuring"
category: "Frontend"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["destructuring", "JS destructuring", "destructuring assignment", "object destructuring", "array destructuring", "rest property"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.89
created_at: 2026-06-23
updated_at: 2026-06-23
review_reason: ""
merge_history: []
tags: ["javascript", "js", "web", "frontend", "w3schools", "destructuring", "es6"]
raw_sources: ["https://www.w3schools.com/js/js_destructuring.asp"]
applied_in: []
github_commit: ""
---

# [[JavaScript Destructuring]]

## 🎯 한 줄 통찰 (One-line insight)
Destructuring assignment unpacks objects and arrays (and any iterable) into individual variables without mutating the original — supporting defaults, aliases, skipping, position picks, and a rest property. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Unpacks objects into variables** — The destructuring assignment syntax can unpack objects into variables. [S1]
- **Order-independent for objects** — When destructuring objects, the order of the properties does not matter. [S1]
- **Non-destructive** — Destructuring is not destructive; it does not change the original object. [S1]
- **Default values** — For potentially missing properties you can set default values. [S1]
- **Property aliases** — A destructured property can be renamed into a different variable name. [S1]
- **Works on any iterable** — Destructuring can be used with any iterables, including strings. [S1]
- **Array picks and skips** — You can pick array variables, skip values with extra commas, and pick by specific index. [S1]
- **Rest property** — Ending a destructuring with a rest property stores all remaining values into a new array. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **`{a, b} = obj`** — Object destructuring binds by property name, in any order. [S1]
- **`{x = default}`** — Supply defaults inline for properties that may be missing. [S1]
- **`{prop : alias}`** — Rename a property into a new variable. [S1]
- **`[a,,,b]`** — Use extra commas to skip array positions. [S1]
- **`{[0]:x ,[1]:y}`** — Pick array values by specific index. [S1]
- **`[a, b, ...rest]`** — Collect remaining array values into `rest`. [S1]
- **`[a, b] = [b, a]`** — Swap two variables in one statement. [S1]

## 📖 세부 내용 (Details)
**Destructuring Assignment Syntax**
The destructuring assignment syntax can unpack objects into variables: [S1]
```javascript
let {firstName, lastName} = person;
```

**Object Destructuring** [S1]
```javascript
// Create an Object
const person = {
  firstName: "John",
  lastName: "Doe",
  age: 50
};

// Destructuring
let {firstName, lastName} = person;
```
The order of the properties does not matter: [S1]
```javascript
// Create an Object
const person = {
  firstName: "John",
  lastName: "Doe",
  age: 50
};

// Destructuring
let {lastName, firstName} = person;
```
Destructuring is not destructive. Destructuring does not change the original object. [S1]

**Object Default Values** — For potentially missing properties we can set default values: [S1]
```javascript
// Create an Object
const person = {
  firstName: "John",
  lastName: "Doe",
  age: 50
};

// Destructuring
let {firstName, lastName, country = "US"} = person;
```

**Object Property Alias** [S1]
```javascript
// Create an Object
const person = {
  firstName: "John",
  lastName: "Doe",
  age: 50
};

// Destructuring
let {lastName : name} = person;
```

**String Destructuring** — One use for destructuring is unpacking string characters. Destructuring can be used with any iterables. [S1]
```javascript
// Create a String
let name = "W3Schools";

// Destructuring
let [a1, a2, a3, a4, a5] = name;
```

**Array Destructuring** — We can pick up array variables into our own variables: [S1]
```javascript
// Create an Array
const fruits = ["Bananas", "Oranges", "Apples", "Mangos"];

// Destructuring
let [fruit1, fruit2] = fruits;
```

**Skipping Array Values** — We can skip array values using two or more commas: [S1]
```javascript
// Create an Array
const fruits = ["Bananas", "Oranges", "Apples", "Mangos"];

// Destructuring
let [fruit1,,,fruit2] = fruits;
```

**Array Position Values** — We can pick up values from specific index locations of an array: [S1]
```javascript
// Create an Array
const fruits = ["Bananas", "Oranges", "Apples", "Mangos"];
// Destructuring
let {[0]:fruit1 ,[1]:fruit2} = fruits;
```

**The Rest Property** — You can end a destructuring syntax with a rest property. This syntax will store all remaining values into a new array: [S1]
```javascript
// Create an Array
const numbers = [10, 20, 30, 40, 50, 60, 70];

// Destructuring
const [a,b, ...rest] = numbers
```

**Destructuring Maps** [S1]
```javascript
// Create a Map
const fruits = new Map([
  ["apples", 500],
  ["bananas", 300],
  ["oranges", 200]
]);

// Destructuring
let text = "";
for (const [key, value] of fruits) {
  text += key + " is " + value;
}
```

**Swapping JavaScript Variables** — You can swap the values of two variables using a destructuring assignment: [S1]
```javascript
let firstName = "John";
let lastName = "Doe";

// Destructuring
[firstName, lastName] = [lastName, firstName];
```

## 🛠️ 적용 사례 (Applied in summary)
The page's own snippets are the canonical applied examples — object/array destructuring, defaults, aliases, string and Map iteration, the rest property, and the variable-swap idiom. No external project/commit applications found in the source.

## 💻 코드 패턴 (Code patterns)
Object destructuring with default and alias (language: JavaScript):
```javascript
let {firstName, lastName, country = "US"} = person;
let {lastName : name} = person;
```
Rest property collects the remainder:
```javascript
const [a, b, ...rest] = numbers;
```
Swap two variables:
```javascript
[firstName, lastName] = [lastName, firstName];
```

## ⚖️ 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:** 0.89
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[JavaScript Tutorial]]
- **관련 개념:** [[JavaScript Object Types Note]], [[JavaScript Type Conversion]], [[JavaScript Introduction]], [[JavaScript NaN]]
- **참조 맥락:** Referenced whenever extracting fields from objects/arrays, setting defaults, or swapping variables in modern (ES6+) JavaScript.

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

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