Reverse Linked List

reverse-ll.js

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var reverseList = function(head) {
  const stack = [];
  let pointer = head;
  let newList;
  let newHead = null;
  while (pointer !== null) {
    stack.push(pointer);
    pointer = pointer.next;
  }
  pointer = null;

  while(stack.length > 0) {
    const node = stack.pop();
    if (newHead === null) {
      newHead = node;
      pointer = newHead;
    } else {
      pointer.next = node;
      pointer = node;
      pointer.next = null;
    }
  }

  return newHead;
};