Largest remainder round

largestRemainderRound.js

/**
 * largestRemainderRound will round each number in an array to the nearest
 * integer but make sure that the the sum of all the numbers still equals
 * desiredTotal. Uses Largest Remainder Method.  Returns numbers in order they
 * came.
 *
 * @param {number[]} numbers - array of numbers
 * @param {number} desiredTotal - denominator: 100 for %, 360 for deg
 * @return {number[]} the list of rounded numbers
 * @example
 *
 * const numbers = [15, 12, 10, 2];
 * largestRemainderRound(numbers, 360)
 * 
 * // => [ 139, 111, 92, 18 ]
 * 
 */

// This modification allows to pass array of not rounded numbers
// and the denominator which is a desired total of the array.
// in case if you want to round up percentages you need to pass 100
// and in case of angles you got to pass 360

const largestRemainderRound = (numbers, desiredTotal) => {
  const _upperSum = numbers.reduce((a, b) => a + b)
  const _sortedArray = numbers.map((number, index) => {
    const _value = (number / _upperSum) * desiredTotal
    return {
      floor: Math.floor(_value),
      remainder: Math.round((_value - Math.floor(_value)) * 10000) / 10000,
      index: index
    }
  }).sort((a, b) => b.remainder - a.remainder)

  const _lowerSum = _sortedArray.reduce((a, b) => a + b.floor, 0)
  for (let i = 0; i < desiredTotal - _lowerSum; i++) {
    _sortedArray[i].floor++;
  }

  return _sortedArray.sort((a, b) => a.index - b.index).map(e => e.floor)
}