2nd/10_Wiki/Topic_JavaScript/JavaScript_Bitwise.md

---
id: javascript-bitwise
title: "JavaScript Bitwise"
category: "Frontend"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["bitwise operators", "bit manipulation", "AND OR XOR", "bit shift", "two's complement", "32-bit operations"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.87
created_at: 2026-06-23
updated_at: 2026-06-23
review_reason: ""
merge_history: []
tags: ["javascript", "js", "web", "frontend", "w3schools", "bitwise", "operators"]
raw_sources: ["https://www.w3schools.com/js/js_bitwise.asp"]
applied_in: []
github_commit: ""
---

# [[JavaScript Bitwise]]

## 🎯 한 줄 통찰 (One-line insight)
JavaScript bitwise operators work bit-by-bit on the binary representation of numbers — even though numbers are stored as 64-bit floats, every bitwise operation is performed on 32-bit binary numbers and returns a standard number. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Seven bitwise operators** — AND (`&`), OR (`|`), XOR (`^`), NOT (`~`), zero fill left shift (`<<`), signed right shift (`>>`), and zero fill right shift (`>>>`). [S1]
- **64-bit storage, 32-bit operations** — JavaScript stores numbers as 64-bit floating point numbers, but all bitwise operations are performed on 32-bit binary numbers. [S1]
- **NOT and signed shift can produce negatives** — `~5` returns `-6`, and `-5 >> 1` returns `-3`, because of two's complement representation. [S1]
- **Bitwise assignment operators** — shift assignments (`<<=`, `>>=`, `>>>=`) and bitwise assignments (`&=`, `^=`, `|=`) combine the operation with assignment. [S1]
- **Base conversion via bitwise** — decimal-to-binary and binary-to-decimal can be done with `(dec >>> 0).toString(2)` and `parseInt(bin, 2).toString(10)`. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Per-bit combination** — `&`, `|`, `^` compare each pair of bits; `~` inverts every bit. [S1]
- **Shift to multiply/divide by powers of two** — `5 << 1` doubles to `10`; `5 >>> 1` halves to `2`. [S1]
- **Unsigned coercion for printing** — `(dec >>> 0)` forces an unsigned 32-bit view before `.toString(2)` to render binary. [S1]

## 📖 세부 내용 (Details)
**Bitwise Operators** — JavaScript provides seven bitwise operators: [S1]

| Operator | Name | Description |
|----------|------|-------------|
| `&` | AND | Sets each bit to 1 if both bits are 1 |
| `\|` | OR | Sets each bit to 1 if one of two bits is 1 |
| `^` | XOR | Sets each bit to 1 if only one of two bits is 1 |
| `~` | NOT | Inverts all the bits |
| `<<` | Zero fill left shift | Shifts left by pushing zeros in from the right and let the leftmost bits fall off |
| `>>` | Signed right shift | Shifts right by pushing copies of the leftmost bit in from the left, and let the rightmost bits fall off |
| `>>>` | Zero fill right shift | Shifts right by pushing zeros in from the left, and let the rightmost bits fall off |

**Note:** JavaScript stores numbers as 64 bits floating point numbers, but all bitwise operations are performed on 32 bits binary numbers. [S1]

**Bitwise AND** — returns `1`: [S1]
```javascript
let x = 5 & 1;
```

**Bitwise OR** — returns `5`: [S1]
```javascript
let x = 5 | 1;
```

**Bitwise XOR** — returns `4`: [S1]
```javascript
let x = 5 ^ 1;
```

**Bitwise NOT** — returns `-6`: [S1]
```javascript
let x = ~5;
```

**Left Shift (`<<`)** — returns `10`: [S1]
```javascript
let x = 5 << 1;
```

**Signed Right Shift (`>>`)** — returns `-3`: [S1]
```javascript
let x = -5 >> 1;
```

**Zero Fill Right Shift (`>>>`)** — returns `2`: [S1]
```javascript
let x = 5 >>> 1;
```

**Operator results summary** (verbatim values from the page) [S1]

| Expression | Result |
|------------|--------|
| `5 & 1` | `1` |
| `5 \| 1` | `5` |
| `5 ^ 1` | `4` |
| `~5` | `-6` |
| `5 << 1` | `10` |
| `-5 >> 1` | `-3` |
| `5 >>> 1` | `2` |

**Bitwise assignment operators** — the page documents shift assignment operators (`<<=`, `>>=`, `>>>=`) and bitwise assignment operators (`&=`, `^=`, `|=`). [S1]

**Converting Decimal to Binary** [S1]
```javascript
function dec2bin(dec){
  return (dec >>> 0).toString(2);
}
```

**Converting Binary to Decimal** [S1]
```javascript
function bin2dec(bin){
  return parseInt(bin, 2).toString(10);
}
```

The page also includes binary-representation tables showing decimal values and their binary form, and two's-complement format for negative numbers. The exact full numeric contents of those tables were not captured verbatim in the fetched source rendering: Not found in source.

## 🛠️ 적용 사례 (Applied in summary)
The page's own snippets are the canonical applied examples — the seven single-operator demonstrations and the `dec2bin` / `bin2dec` conversion helpers. No external project/commit applications found in the source.

## 💻 코드 패턴 (Code patterns)
Single bitwise operations (language: JavaScript):
```javascript
let a = 5 & 1;   // 1
let b = 5 | 1;   // 5
let c = 5 ^ 1;   // 4
let d = ~5;      // -6
let e = 5 << 1;  // 10
let f = -5 >> 1; // -3
let g = 5 >>> 1; // 2
```
Base conversion helpers:
```javascript
function dec2bin(dec){
  return (dec >>> 0).toString(2);
}
function bin2dec(bin){
  return parseInt(bin, 2).toString(10);
}
```

## ⚖️ 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:** 0.87
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[JavaScript Tutorial]]
- **관련 개념:** [[JavaScript Operators]], [[JavaScript Numbers]], [[JavaScript BigInt]], [[JavaScript Number Properties]]
- **참조 맥락:** Referenced when working with flags, masks, low-level math, or base conversions.

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

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