A linked list implementation in JavaScript - Node.js Data Structure

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Description

A linked list implementation in JavaScript

Demo Code


/**/*ww w . j av a 2 s  .  c o m*/
 * A linked list implementation in JavaScript.
 * @class LinkedList
 * @constructor
 */
function LinkedList() {

    /**
     * The number of items in the list.
     * @property _length
     * @type int
     * @private
     */
    this._length = 0;

    /**
     * Pointer to first item in the list.
     * @property _head
     * @type Object
     * @private
     */
    this._head = null;
}

LinkedList.prototype = {

    //restore constructor
    constructor: LinkedList,

    /**
     * Appends some data to the end of the list. This method traverses
     * the existing list and places the value at the end in a new item.
     * @param {variant} data The data to add to the list.
     * @return {Void}
     * @method add
     */
    add: function (data){

        //create a new item object, place data in
        var node = {
                data: data,
                next: null
            },

        //used to traverse the structure
            current;

        //special case: no items in the list yet
        if (this._head === null){
            this._head = node;
        } else {
            current = this._head;

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

            current.next = node;
        }

        //don't forget to update the count
        this._length++;

    },

    /**
     * Retrieves the data in the given position in the list.
     * @param {int} index The zero-based index of the item whose value
     *      should be returned.
     * @return {variant} The value in the "data" portion of the given item
     *      or null if the item doesn't exist.
     * @method item
     */
    item: function(index){

        //check for out-of-bounds values
        if (index > -1 && index < this._length){
            var current = this._head,
                i = 0;

            while(i++ < index){
                current = current.next;
            }

            return current.data;
        } else {
            return null;
        }
    },

    /**
     * Removes the item from the given location in the list.
     * @param {int} index The zero-based index of the item to remove.
     * @return {variant} The data in the given position in the list or null if
     *      the item doesn't exist.
     * @method remove
     */
    remove: function(index){

        //check for out-of-bounds values
        if (index > -1 && index < this._length){

            var current = this._head,
                previous,
                i = 0;

            //special case: removing first item
            if (index === 0){
                this._head = current.next;
            } else {

                //find the right location
                while(i++ < index){
                    previous = current;
                    current = current.next;
                }

                //skip over the item to remove
                previous.next = current.next;
            }

            //decrement the length
            this._length--;

            //return the value
            return current.data;

        } else {
            return null;
        }

    },

    /**
     * Returns the number of items in the list.
     * @return {int} The number of items in the list.
     * @method size
     */
    size: function(){
        return this._length;
    },

    /**
     * Converts the list into an array.
     * @return {Array} An array containing all of the data in the list.
     * @method toArray
     */
    toArray: function(){
        var result = [],
            current = this._head;

        while(current){
            result.push(current.data);
            current = current.next;
        }

        return result;
    },

    /**
     * Converts the list into a string representation.
     * @return {String} A string representation of the list.
     * @method toString
     */
    toString: function(){
        return this.toArray().toString();
    }
};

var list = {};

list = J$.readInput(list);

LinkedList.prototype.add.call(list,3);

console.log(LinkedList.prototype.toString.call(list)+"");

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