--- /dev/null
+var arraySlice = require('../internals/array-slice-simple');
+
+var floor = Math.floor;
+
+var mergeSort = function (array, comparefn) {
+ var length = array.length;
+ var middle = floor(length / 2);
+ return length < 8 ? insertionSort(array, comparefn) : merge(
+ array,
+ mergeSort(arraySlice(array, 0, middle), comparefn),
+ mergeSort(arraySlice(array, middle), comparefn),
+ comparefn
+ );
+};
+
+var insertionSort = function (array, comparefn) {
+ var length = array.length;
+ var i = 1;
+ var element, j;
+
+ while (i < length) {
+ j = i;
+ element = array[i];
+ while (j && comparefn(array[j - 1], element) > 0) {
+ array[j] = array[--j];
+ }
+ if (j !== i++) array[j] = element;
+ } return array;
+};
+
+var merge = function (array, left, right, comparefn) {
+ var llength = left.length;
+ var rlength = right.length;
+ var lindex = 0;
+ var rindex = 0;
+
+ while (lindex < llength || rindex < rlength) {
+ array[lindex + rindex] = (lindex < llength && rindex < rlength)
+ ? comparefn(left[lindex], right[rindex]) <= 0 ? left[lindex++] : right[rindex++]
+ : lindex < llength ? left[lindex++] : right[rindex++];
+ } return array;
+};
+
+module.exports = mergeSort;