归并排序法

1.之前在网上看到一个很有思想的算法，学习一下，然后代码保存下来，已经忘了出处，有知道的可以提示我。
 1 <!DOCTYPE html>
 2 <html>
 3     <head>
 4         <meta charset="UTF-8">
 5         <title></title>
 6     </head>
 7     <body>
 8         <script>
 9 var mergeSort = (function() {
10     // 合并
11     var _merge = function(left, right, prop) {
12         var result = [];
13  
14         // 对数组内成员的某个属性排序
15         if (prop) {
16             while (left.length && right.length) {
17                 if (left[0][prop] <= right[0][prop]) {
18                     result.push(left.shift());
19                 } else {
20                     result.push(right.shift());
21                 }
22             }
23         } else {
24             // 数组成员直接排序
25             while (left.length && right.length) {
26                 if (left[0] <= right[0]) {
27                     result.push(left.shift());
28                 } else {
29                     result.push(right.shift());
30                 }
31             }
32         }
33  
34         while (left.length)
35             result.push(left.shift());
36  
37         while (right.length)
38             result.push(right.shift());
39  
40         return result;
41     };
42  
43     var _mergeSort = function(arr, prop) { // 采用自上而下的递归方法
44         var len = arr.length;
45         if (len < 2) {
46             return arr;
47         }
48         var middle = Math.floor(len / 2),
49             left = arr.slice(0, middle),
50             right = arr.slice(middle);
51         return _merge(_mergeSort(left, prop), _mergeSort(right, prop), prop);
52     };
53  
54     return function(arr, prop, order) {
55         var result = _mergeSort(arr, prop);
56         if (!order || order.toLowerCase() === 'asc') {
57             // 升序
58             return result;
59         } else {
60             // 降序
61             var _ = [];
62             result.forEach(function(item) {
63                 _.unshift(item);
64             });
65             return _;
66         }
67     };
68 })();
69 
70                var arr = [{"name":"zhangsan","age":19},{"name":"lisi","age":20},{"name":"wangwu","age":15},{"name":"wangwu","age":14},{"name":"wangwu","age":17}];
71               console.log(mergeSort(arr,'age'));
72         </script>
73     </body>
74 </html>