function mergeSort(arr) {
if (arr.length > 1) {
let mid = Math.floor(arr.length/2)
let left = arr.slice(0, mid)
let right = arr.slice(mid, arr.length)
let leftSorted = mergeSort(left)
let rightSorted = mergeSort(right)
let res = mergeArrays(leftSorted, rightSorted)
return res
}
return arr
}