Bit Manipulation Basics

Written by Swapnil RajaPublished 28 Aug 2026

Bit tricks are rarely the right tool in application code and are asked about constantly in interviews. Learn the handful that come up; resist using them where a boolean would read better.

The operators

What each one does

javascript

// AND — 1 only where both are 1
console.log(0b1100 & 0b1010)   // 0b1000 = 8

// OR — 1 where either is 1
console.log(0b1100 | 0b1010)   // 0b1110 = 14

// XOR — 1 where they differ
console.log(0b1100 ^ 0b1010)   // 0b0110 = 6

// NOT — flips every bit (and the sign)
console.log(~5)                // -6

// Shifts — multiply and divide by powers of two
console.log(5 << 1)            // 10
console.log(5 >> 1)            // 2

PreviousGreedy vs Dynamic Programming NextMatrix Traversal and Manipulation

Find the unpaired number

javascript

// Every number appears twice except one. O(n) time, O(1) space.
function singleNumber(nums) {
  let result = 0
  for (const n of nums) result ^= n
  return result
}

console.log(singleNumber([4, 1, 2, 1, 2]))  // 4

// Swap without a temporary — a party trick, not production code.
let a = 3, b = 7
a ^= b; b ^= a; a ^= b
console.log(a, b)  // 7 3

Worth recognising

javascript

// Even or odd — faster than % 2 and clearer once you know it.
const isEven = (n) => (n & 1) === 0

// Power of two? Exactly one bit set.
const isPowerOfTwo = (n) => n > 0 && (n & (n - 1)) === 0

// Count the set bits.
function countBits(n) {
  let count = 0
  while (n) {
    n &= n - 1        // clears the lowest set bit
    count++
  }
  return count
}

console.log(isPowerOfTwo(16))  // true
console.log(countBits(0b1011)) // 3

Where it breaks

javascript

console.log(2 ** 31)          // 2147483648 — fine as a number
console.log((2 ** 31) | 0)    // -2147483648 — wraps to negative

console.log(1 << 31)          // -2147483648
console.log(1 << 32)          // 1 — the shift wrapped around

// Use BigInt when you genuinely need more than 32 bits.
console.log(1n << 32n)        // 4294967296n

Bit Manipulation Basics

The operators

XOR, the one worth knowing

Checking and setting bits

Tricks that come up

The 32-bit trap