add 876 js solution

Author: swiftwind0405

README.md

@@ -49,7 +49,7 @@
 |922|[Sort Array By Parity II](https://leetcode.com/problems/sort-array-by-parity-ii/) | |Easy|
 |914|[X of a Kind in a Deck of Cards](https://leetcode.com/problems/x-of-a-kind-in-a-deck-of-cards/) | |Easy|
 |905|[Sort Array By Parity](https://leetcode.com/problems/sort-array-by-parity/) | |Easy|
-|876|[Middle of the Linked List](https://leetcode.com/problems/middle-of-the-linked-list/) | |Easy|
+|876|[Middle of the Linked List](https://leetcode.com/problems/middle-of-the-linked-list/) | [js](./algorithms/middleOfTheLinkedList/Solution.js) |Easy|
 |859|[Buddy Strings](https://leetcode.com/problems/buddy-strings/description/) | |Easy|
 |858|[Mirror Reflection](https://leetcode.com/problems/mirror-reflection/description/) | |Medium|
 |852|[Peak Index in a Mountain Array](https://leetcode.com/problems/peak-index-in-a-mountain-array/description/) | |Easy|

algorithms/middleOfTheLinkedList/Solution.js

@@ -0,0 +1,28 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {ListNode}
+ */
+var middleNode = function(head) {
+    const list = [];
+    const loop = (node) => {
+        list.push(node)
+        if (node.next) {
+            loop(node.next)
+        }
+    }
+    loop(head)
+    const middle = list.length/2
+    // 如果中位数是整数
+    if (middle%1 === 0) {
+        return list[middle];
+    } else {
+        return list[Math.round(middle)-1]
+    }
+};