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Bitwise Operators

Bitwise operators treat numbers as 32-bit binary sequences and operate on them bit by bit. They include AND (&), OR (|), XOR (^), NOT (~), left shift (<<), right shift (>>), and unsigned right shift (>>>). These are rarely needed in typical web development but appear in performance-sensitive code, flags/permissions systems, and low-level algorithms.

Syntax

a & b, a | b, a ^ b, ~a, a << b, a >> b

Examples

Basic Bitwise Operations

How bitwise operators manipulate binary representations of numbers.

console.log(5 & 1);  // 1  (0101 & 0001 = 0001)
console.log(5 | 1);  // 5  (0101 | 0001 = 0101)
console.log(5 ^ 1);  // 4  (0101 ^ 0001 = 0100)
console.log(~5);     // -6 (bitwise NOT inverts all bits)
console.log(5 << 1); // 10 (shifts bits left, doubling the value)
console.log(5 >> 1); // 2  (shifts bits right, halving and flooring)

Using Bitwise Flags

A common real-world use case: combining permission flags into a single number.

const READ = 1;   // 001
const WRITE = 2;  // 010
const EXECUTE = 4; // 100

const userPermissions = READ | WRITE; // 011 (3)

const canWrite = (userPermissions & WRITE) !== 0;
console.log(canWrite); // true

Best practices

  • Reach for bitwise operators only when you have a genuine binary/flag-based use case - they hurt readability otherwise
  • Do not confuse & and | with the logical && and || operators - they behave very differently
  • Use Number.isInteger() checks before bitwise operations, since they implicitly convert operands to 32-bit integers
  • Document flag-based bitwise code clearly, since it is one of the least intuitive parts of JavaScript for most readers

Runtime & versions

Browsers and JavaScript runtimes. Feature availability depends on the language and runtime version used by your project; consult the official reference below.

ECMAScript specification

Specifications & further reading