let results = [];

let i = 0;

let j = 0;

while(i < arr1.length && j < arr2.length){

    if(arr2[j] > arr1[i]){

        results.push(arr1[i]);

        i++;

    } else {

        results.push(arr2[j]);

        j++;

    }

}

while(i < arr1.length) {

    results.push(arr1[i]);

    i++;

}

while(j < arr2.length) {

    results.push(arr2[j]);

    j++;

}

return results;

if(arr.length <= 1) return arr;

let mid = Math.floor(arr.length/2);

let left = mergeSort(arr.slice(0,mid));

let right = mergeSort(arr.slice(mid));

return merge(left,right);