Javascript: Merge Sort Implementation

Merge sort works by divide the unsorted list into n sublists, where n is the number of elements in the list. That being said it divides the list into n lists and each only contain one element. One element is considered sorted, thus we get n sorted lists. With the n sorted lists, then repeatedly merge them to produce new sublists until there is only 1 list remaining and that will be the sorted list.
Here is an example of merge sort using Javascript

function mergeSort(data)
{
    if(data.length == 1 ) return data;
 
    var mid = data.length / 2;
    var left = data.slice(0, mid);
    var right = data.slice(mid);
 
    left = mergeSort(left);
    right = mergeSort(right);
     
    return merge(left, right);
}
 
function merge(left, right)
{
    var result=[];
    var leftIndex=0;
    var rightIndex=0;
 
    while(leftIndex<left.length && rightIndex<right.length)
    {
        if(left[leftIndex]>right[rightIndex])
        {
 
            result.push(right[rightIndex]);
            rightIndex++;
        }
        else
        {
            result.push(left[leftIndex]);
            leftIndex++;
        }
    }
    while(leftIndex<left.length)
    {
        result.push(left[leftIndex]);
        leftIndex++;
    }
    while(rightIndex<right.length)
    {
        result.push(right[rightIndex]);
        rightIndex++;
    }
    return result;
}