class LinkedListNode {

  constructor(val, next = null) {

    this.val = val;

    this.next = next;

  }

}

​

l1 = new LinkedListNode(8);

l2 = new LinkedListNode(4);

l1.next = l2;

​

function reverseList(head) {

  if (!head || !head.next) {

    return head;

  }

​

  let rest = reverseList(head.next);

​

  head.next.next = head;

  delete head.next;

  return rest;

}

​

console.log(reverseList(l1));