Doubly Linked List

doubly_linked_list.js

var Node = function ( data ) {
    
  this.data = data;
  this.next = null;
  this.previous = null;
}

var LinkedList = function () {

  this.first = null;
  this.last = null;
  this.length = 0;
}

LinkedList.prototype = {

  append: function ( data ) {

    var node = new Node( data );
    if ( this.first != null ) {
      this.last.next = node
      node.previous = this.last
      this.last = node;
    }
    else {
      this.first = node;
      this.last = node;
    }
    this.length++ ;
  },

  remove: function ( node ) {

    var previous = node.previous,
      next = node.next;

    if ( previous !== null && next !== null ) {
      previous.next = next;
      next.previous = previous;
    }
    else if ( previous === null && next !== null ) {
      this.first = next;
      next.previous = null;
    }
    else if ( previous !== null && next === null ) {
      this.last = previous;
      previous.next = null;
    }
    else {
      this.first = null;
      this.last = null;
    }
    this.length-- ;
  }
}