JavaScript版的TwoQueues缓存模型

var tq = initTwoQueues(10, true);
tq.hitRatio();

 (function(exports){
     /**
      * 继承用的纯净类
      * @constructor
      */
     function Fn(){}
     Fn.prototype = Elimination.prototype;
     /**
      * 基于链表的缓存淘汰算法父类
      * @param maxLength 缓存容量
      * @constructor
      */
     function Elimination(maxLength){
         this.container = {};
         this.length = 0;
         this.maxLength = maxLength || 30;
         this.linkHead = this.buildNode("", "");
         this.linkHead.head = true;
         this.linkTail = this.buildNode("", "");
         this.linkTail.tail = true;
         this.linkHead.next = this.linkTail;
         this.linkTail.prev = this.linkHead;
     }
     Elimination.prototype.get = function(key){
         throw new Error("This method must be override!");
     };
     Elimination.prototype.set = function(key, value){
         throw new Error("This method must be override!");
     };
     /**
      * 创建链表中的节点
      * @param data 节点包含的数据，即缓存数据值
      * @param key 节点的唯一标示符，即缓存的键
      * @returns {{}}
      */
     Elimination.prototype.buildNode = function(data, key){
         var node = {};
         node.data = data;
         node.key = key;
         node.use = 0;
         return node;
     };
     /**
      * 从链表头弹出一个节点
      * @returns {*}
      */
     Elimination.prototype.shift = function(){
         var node = null;
         if(!this.linkHead.next.tail){
             node = this.linkHead.next;
             this.linkHead.next = node.next;
             node.next.prev = this.linkHead;
             delete this.container[node.key];
             this.length--;
         }
         return node;
     };
     /**
      * 从链表头插入一个节点
      * @param node 节点对象
      * @returns {*}
      */
     Elimination.prototype.unshift = function(node){
         node.next = this.linkHead.next;
         this.linkHead.next.prev = node;
         this.linkHead.next = node;
         node.prev = this.linkHead;
         this.container[node.key] = node;
         this.length++;
         return node;
     };
     /**
      * 从链表尾插入一个节点
      * @param node 节点对象
      * @returns {*}
      */
     Elimination.prototype.append = function(node){
         this.linkTail.prev.next = node;
         node.prev = this.linkTail.prev;
         node.next = this.linkTail;
         this.linkTail.prev = node;
         this.container[node.key] = node;
         this.length++;
         return node;
     };
     /**
      * 从链表尾弹出一个节点
      * @returns {*}
      */
     Elimination.prototype.pop = function(){
         var node = null;
         if(!this.linkTail.prev.head){
             node = this.linkTail.prev;
             node.prev.next = this.linkTail;
             this.linkTail.prev = node.prev;
             delete this.container[node.key];
             this.length--;
         }
         return node;
     };
     /**
      * 从链表中移除指定节点
      * @param node 节点对象
      * @returns {*}
      */
     Elimination.prototype.remove = function(node){
         node.prev.next = node.next;
         node.next.prev = node.prev;
         delete this.container[node.key];
         this.length--;
         return node;
     };
     /**
      * 节点被访问需要做的处理，具体是把该节点移动到链表头
      * @param node
      */
     Elimination.prototype.use = function(node){
         this.remove(node);
         this.unshift(node);
     };
 
     /**
      * LRU缓存淘汰算法实现
      * @constructor
      */
     function LRU(){
         Elimination.apply(this, arguments);
     }
     LRU.prototype = new Fn();
     LRU.prototype.get = function(key){
         var node = undefined;
         node = this.container[key];
         if(node){
             this.use(node);
         }
         return node;
     };
     LRU.prototype.set = function(key, value){
         var node = this.buildNode(value, key);
         if(this.length === this.maxLength){
             this.pop();
         }
         this.unshift(node);
     };
 
     /**
      * FIFO缓存淘汰算法实现
      * @constructor
      */
     function FIFO(){
         Elimination.apply(this, arguments);
     }
     FIFO.prototype = new Fn();
     FIFO.prototype.get = function(key){
         var node = undefined;
         node = this.container[key];
         return node;
     };
     FIFO.prototype.set = function(key, value){
         var node = this.buildNode(value, key);
         if(this.length === this.maxLength){
             this.shift();
         }
         this.append(node);
     };
 
     /**
      * LRU、FIFO算法封装，成为新的twoqueues缓存淘汰算法
      * @param maxLength
      * @constructor
      */
     function Agent(maxLength){
         this.getCount = 0;
         this.hitCount = 0;
         this.lir = new FIFO(maxLength);
         this.hir = new LRU(maxLength);
     }
     Agent.prototype.get = function(key){
         var node = undefined;
         node = this.lir.get(key);
         if(node){
             node.use++;
             if(node.use >= 2){
                 this.lir.remove(node);
                 this.hir.set(node.key, node.data);
             }
         }else{
             node = this.hir.get(key);
         }
         return node;
     };
     Agent.prototype.getx = function(key){
         var node = undefined;
         this.getCount++;
         node = this.get(key);
         if(node){
             this.hitCount++;
         }
         return node;
     };
     Agent.prototype.set = function(key, value){
         var node = null;
         node = this.lir.container[key] || this.hir.container[key];
         if(node){
             node.data = value;
         }else{
             this.lir.set(key, value);
         }
     };
     /**
      * 获取命中率
      * @returns {*}
      */
     Agent.prototype.hitRatio = function(){
         var ret = this.getCount;
         if(ret){
             ret = this.hitCount / this.getCount;
         }
         return ret;
     };
     /**
      * 对外接口
      * @param maxLength 缓存容量
      * @param dev 是否为开发环境，开发环境会统计命中率，反之不会
      * @returns {{get, set: Function, hitRatio: Function}}
      */
     exports.initTwoQueues = function(maxLength, dev){
         var api = new Agent(maxLength);
         return {
             get: (function(){
                 if(dev){
                     return function(key){
                         var ret = api.getx(key);
                         return ret && ret.data;
                     };
                 }else{
                     return function(key){
                         var ret = api.get(key);
                         return ret && ret.data;
                     };
                 }
             }()),
             set: function(){
                 api.set.apply(api, arguments);
             },
             hitRatio: function(){
                 return api.hitRatio.apply(api, arguments);
             }
         };
     };
 
 }(this));