数据结构-栈，队列，链表，树

 1 class ListNode {
 2     constructor(key = null, next = null) {
 3         this.key = key;
 4         this.next = next;
 5     }
 6 
 7     push(next) {
 8         this.next = next;
 9         return next;
10     }
11 
12     reverse() {
13         if (this.key !== null) {
14             console.log("不是NIL");
15             return;
16         }
17         var Nil = this;
18         var pre = this.next;
19         var cur = pre.next;
20         pre.next = null;
21         while (cur !== null) {
22             console.log("pre:", pre.key, "cur:", cur.key);
23             var next = cur.next;
24             cur.next = pre;
25             pre = cur;
26             cur = next;
27         }
28         Nil.next = pre;
29         return Nil;
30     }
31 
32     toStirng() {
33         var cur = this;
34         while (cur != null) {
35             if (cur.next) {
36                 console.log("the key of this ListNode is: ", cur.key, "the next of this ListNode is: ", cur.next.key);
37 
38             } else {
39                 console.log("the key of this ListNode is: ", cur.key, "the next of this ListNode is: null");
40             }
41             cur = cur.next;
42         }
43     }
44 }
45 
46 
47 var NIL = new ListNode();
48 
49 var first = new ListNode(1);
50 
51 var second = new ListNode(2);
52 
53 var third = new ListNode(3);
54 
55 
56 NIL.push(first).push(second).push(third);
57 
58 var temp = NIL.next;
59 
60 NIL.reverse().toStirng();
这是前序遍历