允许从队列两端添加和删除元素，因此也叫双向队列。
function Deque() {this.dataStore = [];//进队列，从尾部添加数据this.enqueue = function (data) {var length = this.length();this.dataStore[length] = data;}//进队列，从头部添加数据this.enqueuehead = function (data) {var length = this.length();for(var i=length;i>=1;i--) {this.dataStore[i] = this.dataStore[i-1];}this.dataStore[0] = data;}//从队列头部删除数据，并且获得这个数据this.dequeue=function () {var length = this.length();var front = this.dataStore[0];for(var i=1;i<length;i++) {this.dataStore[i-1] = this.dataStore[i];}this.dataStore[length-1] = null;this.dataStore.length--;return front;}//从队列尾部删除数据，并且获得这个数据this.dequeueback=function () {var length = this.length();var back = this.dataStore[length-1];this.dataStore[length-1] = null;this.dataStore.length--;return back;}//依次返回当前队列的数据this.toString=function () {return this.dataStore.toString();}//获得队列最前面的数据this.front=function(){return this.dataStore[0];}//获得队列最后面的数据this.back=function () {return this.dataStore[this.dataStore.length-1];}//判断当前队列是否为空this.empty=function () {if(this.dataStore.length==0){return true;}else{return false;}}//获取队列的长度this.length = function () {return this.dataStore.length;}//遍历队列this.forEach = function (call) {//获得队列的长度var length = this.length();for(var i=0;i<length;i++) {call(this.dataStore[i]);}}
}