--- id: 587d8251367417b2b2512c64 title: Search within a Linked List challengeType: 1 forumTopicId: 301715 --- ## Description

Let's add a few more useful methods to our linked list class. Wouldn't it be useful if we could tell if our list was empty or not, as with our Stack and Queue classes? We should also be able to find specific elements in our linked list. Traversing through data structures is something you'll want to get a lot of practice with! Let's create an indexOf method that takes an element as an argument, and returns that element's index in the linked list. If the element is not found in the linked list, return -1. Let's also implement a method that does the opposite: an elementAt method that takes an index as an argument and returns the element at the given index. If no element is found, return undefined.

## Instructions

Write an isEmpty method that checks if the linked list is empty, an indexOf method that returns the index of a given element, and an elementAt that returns an element at a given

index.



## Tests


```yml
tests:
  - text: Your LinkedList class should have a indexOf method.
    testString: assert((function(){var test = new LinkedList(); return (typeof test.indexOf === 'function')}()));
  - text: Your LinkedList class should have a elementAt method.
    testString: assert((function(){var test = new LinkedList(); return (typeof test.elementAt === 'function')}()));
  - text: Your size method should return the length of the linked list
    testString: assert((function(){var test = new LinkedList(); test.add('cat'); test.add('dog'); test.add('kitten'); return test.size() === 3}()));
  - text: Your indexOf method should return the index of the given element.
    testString: assert((function(){var test = new LinkedList(); test.add('cat'); test.add('dog'); test.add('kitten'); return test.indexOf('kitten') === 2}()));
  - text: Your elementAt method should return at element at a given index.
    testString: assert((function(){var test = new LinkedList(); test.add('cat'); test.add('dog'); test.add('kitten'); return test.elementAt(1) === 'dog'}()));

```



## Challenge Seed




```js
function LinkedList() {
  var length = 0;
  var head = null;

  var Node = function(element){ // {1}
    this.element = element;
    this.next = null;
  };

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

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

  this.add = function(element){
    var node = new Node(element);
    if(head === null){
        head = node;
    } else {
        var currentNode = head;

        while(currentNode.next){
            currentNode  = currentNode.next;
        }

        currentNode.next = node;
    }

    length++;
  };

  this.remove = function(element){
    var currentNode = head;
    var previousNode;
    if(currentNode.element === element){
        head = currentNode.next;
    } else {
        while(currentNode.element !== element) {
            previousNode = currentNode;
            currentNode = currentNode.next;
        }

        previousNode.next = currentNode.next;
    }

    length --;
  };

  // Only change code below this line

  // Only change code above this line
}
```





## Solution


```js
// solution required
```