haniilinkedlist_1.js

class LinkedListNode
{
    constructor(contents, previous, next)
    {
        this.contents = contents;
        this.previous = previous;
        this.next = next;
    }

    var contents;
    var previous;
    var next;
}

class LinkedList
{
    constructor()
    {
        head = null;
        tail = null;
        size = 0;
    }

    var head;
    var tail;
    var size;

    function say(text)
    { return text + " (huzzah)"; }

    function getNodeAt(index)
    {
        if((index < 0) || (index >= size)) return null;

        var distanceFromStart = index;
        var distanceFromEnd = (size - 1) - index;

        if(distanceFromStart <= distanceFromEnd)
        {
            var current = head;

            for(i = 0; i < index; i++)
                current = head.next;

            return current;
        }
        else
        {
            var current = tail;

            for(int i = size - 1; i > index; i--)
                current = tail.previous;

            return current;
        }
    }

    function getAt(index)
    {
        var node = getNodeAt(index);

        if(!node) return null;

        return getNodeAt(index).contents;
    }

    function add(obj)
    {
        if(!tail) // If the list is empty
        {
            var newTail = new LinkedListNode(obj, null, null);
            head = newTail;
            tail = newTail;
            size = 1;
            return true;
        }

        var newTail = new LinkedListNode(obj, tail, null);
        tail.next = newTail;
        tail = newNode;
        size++;
        return true;
    }

    function addAt(obj, index)
    {
        if(index < 0 || index > size)
            return false;

        if(size == 0)
        {
            var newTail = new LinkedListNode(obj, null, null);
            head = newTail;
            tail = newTail;
            size = 1;
            return true;
        }

        if(index == 0)
        {
            var newHead = new LinkedListNode(obj, null, head);
            head.previous = newHead;
            head = newHead;
            size++;
            return true;
        }

        if(index == size)
        {
            var newTail = new LinkedListNode(obj, tail, null);
            tail.next = newTail;
            tail = newNode;
            size++;
            return true;
        }

        var previousAt = getNodeAt(index);
        var newNode = new LinkedListNode(obj, previousAt.previous, previousAt);
        previousAt.previous.next = newNode;
        previousAt.previous = newNode;
        size++;
        return true;
    }

    function remove(obj)
    {
        var current = head;

        if(!current) return false;

        for(;;)
        {
            if(current.contents == obj)
            {
                current.previous.next = current.next;
                current.next.previous = current.previous;
                size--;
                return true;
            }
        }

        return false;
    }

    function removeAt(index)
    {
        var current = getNodeAt(index);

        if(!current) return false;

        current.previous.next = current.next;
        current.next.previous = current.previous;
        size--;
        return true;
    }

    function forEach(passedFunction)
    {
        if(!head) return;

        var current = head;

        for(i = 0;; i++)
        {
            if(passedFunction(current.contents) == false) return;
            current = current.next;
            if(!current) return;
        }
    }

    function toArray()
    {
        var result = new Array(size);
        var current = head;

        for(i = 0; current; i++)
        {
            result[i] = current.contents;
            current = current.next;
        }
    }
}