Check if a number is a power of 2

Use the bit trick n & (n − 1) on a positive integer.

JavaScript Version 1.0.0 · MIT · .md

function isPowerOfTwo(n) { return n > 0 && (n & (n - 1)) === 0; }

Input & expected output

64

true

The edge case

0

false

Know the limits

• The original returned true for 0; this version requires n > 0.
• Bitwise operators use 32-bit integers, so the lab accepts 0 to 2^30.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

• Check whether all values are equal — Compare every item with the first using Object.is.
• Check whether an object is empty — Check for own enumerable string keys on a JSON object.
• Check whether an integer is even — Test parity for safe integers, including zero and negative values.