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();