Javascript Linked List

linkedlist.js

function ll(){
  this.last = this.first = null;
  
  this.add = function(value){
    node = {value: value, next: null, prev: this.last};
    this.first = this.first ? this.first : node;
    if(this.last) this.last.next = node;
    this.last = node;
    return node;
  };
  
  this.remove = function(node){
    if(node.prev) node.prev.next = node.next;
    if(node.next) node.next.prev = node.prev;
    return node.value;
  };
  
  return this;
}