JavaScript - Bitwise Operations Part 2: Bitwise AND (&)

How the AND (&) Operator Works

The AND operator compares two binary numbers bit by bit and returns 1 only if both corresponding bits are 1. Otherwise, it returns 0.

Example 1: AND Operation

console.log(5 & 3); // Output: 1

Explanation:

Binary representation:

5  =  101

3  =  011

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Result = 001  (1 in decimal)

Only the last bit matches (1 & 1 = 1), so the result is 1.

Example 2: Using AND for Permissions

Bitwise AND is often used for permission checks.

const READ = 4;  // 100

const WRITE = 2; // 010

const EXECUTE = 1; // 001

let userPermissions = READ | WRITE; // 100 | 010 = 110 (6)

console.log(userPermissions & READ);   // 4 (has READ permission)

console.log(userPermissions & EXECUTE); // 0 (no EXECUTE permission)

Explanation:

userPermissions has READ and WRITE, but not EXECUTE.

AND (&) checks if a specific permission exists.