failing sort

fail_sort

function splitList(list){
    var both = [ [],[] ]
    var arr;
    var left = []
	var right = []
	var middle = Math.ceil(list.length / 2)
	for (var i = 0; i < middle; i++) {
		both[0].push(list[i]);
	}
	for (var j = middle; j < list.length; j++) {
		both[1].push(list[j]);
	}
	return both
}
function merge(arr1, arr2) {
    
   new_arr = arr1.concat(arr2)
   console.log(new_arr)
   return new_arr.sort()
}
function mergeSort(list){

	if (list.length == 1){
		return list
	}
    var both = splitList(list)
    
    //console.log(both[1])
    
	left = mergeSort(both[0])
 	right = mergeSort(both[1])
	return merge(left, right)
}