merge-sort algorithm using Javascript

merge-sort.js

const numbers = [99, 44, 6, 2, 1, 5, 63, 87, 283, 4, 0];

function mergeSort(array) {
  if (array.length === 1) {
    return array
  }

  let half = array.length / 2
  let left = array.slice(0, half)
  let right = array.slice(half)
  return merge(
    mergeSort(left),
    mergeSort(right)
  )
}

function merge(left, right) {
  let result = []
  let leftIndex = 0
  let rightIndex = 0

  while(leftIndex < left.length && rightIndex < right.length) {
    if (left[leftIndex] < right[rightIndex]) {
      result.push(left[leftIndex])
      leftIndex++
    }else {
      result.push(right[rightIndex])
      rightIndex++
    }
  }
  
  return result.concat(left.slice(leftIndex), right.slice(rightIndex))
}


mergeSort(numbers)