feat: add question 206

Author: yinxin630

206.反转链表.js

@@ -0,0 +1,35 @@
+/*
+ * @lc app=leetcode.cn id=206 lang=javascript
+ *
+ * [206] 反转链表
+ */
+
+// @lc code=start
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {ListNode}
+ */
+var reverseList = function(head) {
+    if (!head) {
+        return null;
+    }
+
+    let result = head;
+    head = head.next;
+    result.next = null;
+    while (head) {
+        const next = head.next;
+        head.next = result;
+        result = head;
+        head = next;
+    }
+    return result;
+};
+// @lc code=end