/* ======================================== LRU 最近最少使用 ======================================== */
	function FifoCache(limit){
		limit = limit||10;
		var _store = [];
		var index = {};
		this.get = function(key){
			var ind = index[key];
			return _store[ind];
		};
		 
		this.set = function(key,value){
			if(_store.length>=limit){
				_store.shift();
			
				for(var k in index){
					index[k] = index[k]-1;
				} 
			}
			 
			var length = _store.push(value);
			index[key] = length-1;
		};
		 
		this.list = function(){
			console.log(_store);
		};     
	}

js 簡單實現FIFO