问Javascript：实现一个算法来找到单个链接字符串的Kth到最后一个元素？

EN

function LinkedList() {
  let length = 0;
  let head = null;

  function Node(element) {
    this.element = element;
    this.next = null;
  }

  this.length = function() {
    return length;
  }

  this.head = function() {
    return head;
  }

  this.add = function(element) {
    let node = new Node(element);

    if (head == null) {
      head = node;
    } else {
      currentNode = head;

      while (currentNode.next) {
        currentNode = currentNode.next;
      }
      currentNode.next = node;
    }
    length++;
  }

  this.findLast = function(index) {
    if(index > length) {
      return false;
    }
    if (index < 0) {
      return false;
    }

    let realIndexes = length-1; // if length = 5, realIndexes = 4
    let realPosition = index-1; // if index = 2, realPosition = 1 
    // We are looking for the real position here.
    let realTarget = realIndexes - realPosition;
    let currentNode = head;
    let counter = 0;

    while (counter < realTarget) {
      currentNode = currentNode.next;
      counter++;
    }
    return currentNode.element;
  }
}

let congo = new LinkedList();
console.log(congo)
congo.add(5);
congo.add("Homeless");
congo.add("Real eyes realize real lies");
congo.length()
congo.head()