super-simple-linked-list.js

const LinkedList = () => {
  let length = 0;
  let headNode = null;

  let Node = (element) => ({
    element,
    next: null,
  });

  let size = () => length;
  let head = () => headNode;
  let add = (element) => {
    let node = Node(element);
    if (headNode === null) {
      headNode = node;
    } else {
      let currentNode = headNode;
      while (currentNode.next) {
        currentNode = currentNode.next;
      }
      currentNode.next = node;
    }
    length++;
  };

  return {
    size,
    head,
    add,
  };
};

let cities = LinkedList();
cities.add('ankara');
cities.add('milano');
cities.add('berlin');
console.log(cities.size() === 3);

let animals = LinkedList();
animals.add('lion');
animals.add('elephant');
console.log(animals.head().element === 'lion');