Problem 8/30 of LeetCode 30-day challenge

middleNode.js

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */

let middleNode = function(head) {
  let length = 1;
  let currentNode = head;
  // node to return
  let targetNode;
  while(currentNode.next !== null){
    // counts the length of the linkedlist
    length++;
    currentNode = currentNode.next;
  }
  // case for just one node
  if(length === 1){
    return head;
  }
  
  /* 
  * if the length is even, add 1 to mid 
  * to handle case for two middle nodes
  */
  let mid = length % 2 === 0 ? Math.ceil(length / 2) + 1 : Math.ceil(length / 2);
  let i = 1;
  let node = head;
  // while loop, but make it for
  while((node.next !== null) && i < length) {
    node = node.next;
    i++;
    if(i === mid){
      targetNode = node;
    }
  }
  return targetNode;
};