Create Array From Bitmask

bitmask-to-array.mjs

/**
 * Convert a bitmask to an array of its individual bits
 *
 * @param {number} bitmask The bitmask to dissect
 * @return {number[]}
 *
 * @example
 * assert.equal(bitmaskToArray(0b101), [0b100, 0b001])
 */
export function bitmaskToArray(bitmask) {
  if (!Number.isInteger(bitmask) || bitmask < 0) {
    throw new TypeError(`Bitmask needs to be a non-negative integer, got ${bitmask}`)
  }

  let array = []
  let upperBoundOrder = 0
  while (2 ** upperBoundOrder <= bitmask) {
    let upperBound = 2 ** upperBoundOrder
    if (upperBound & bitmask) {
      array.push(upperBound)
    }
    upperBoundOrder++
  }

  return array
}