Question

How to round a number to the nearest power of 2 in JavaScript

Answer 1

/**
 * Rounds a positive integer to the nearest power of 2.
 * returns the nearest power of 2
 */
function roundToNearestPowerOf2(n) {
  if (n <= 0) return 0;

  let prevPower = 1;
  while (prevPower * 2 <= n) {
    prevPower *= 2;
  }

  const nextPower = prevPower * 2;
  return (n - prevPower < nextPower - n) ? prevPower : nextPower;
}

const num = 37;

console.log(`Nearest power of 2: ${roundToNearestPowerOf2(num)}`);



/*
run:

Nearest power of 2: 32

*/

 

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Answer 2

function roundToNearestPowerOf2(n) {
  if (n <= 0) return 0;

  // Compute the previous power of 2 using bit length
  const prevPower = 1 << (Math.floor(Math.log2(n)));

  // Compute the next power of 2
  const nextPower = prevPower << 1;

  // Return the one closest to n
  return (n - prevPower < nextPower - n) ? prevPower : nextPower;
}

const num = 37;

console.log(`Nearest power of 2: ${roundToNearestPowerOf2(num)}`);




/*
run:

Nearest power of 2: 32

*/

 

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