reverse-linked-list.js

/**Given the head of a singly linked list, reverse the list, and return the reversed list. */
/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
 var reverseList = function(head) {
    let current = head,
      prev = null,
      next = null;
  
    while (current) {
      next = current.next;
      current.next = prev;
      prev = current;
      current = next;
    }
  
    return prev;
  };