javascript中的双向队列

/*--------------双向Queue类的定义和测试代码----------------*/
function Queue(){
        this.dataStore = [];
        this.enqueueFront = enqueueFront;
        this.enqueueBack = enqueueBack;
        this.dequeueFront = dequeueFront;
        this.dequeueBack = dequeueBack;
        this.front = front;
        this.back = back;
        this.toString = toString;
        this.empty = empty;
}

//尾部入队，就是在数组的末尾添加一个元素
function enqueueBack(element){
    this.dataStore.push(element);
}

//头部入队，就是在数组的头部添加一个元素
function enqueueFront(element){
    this.dataStore.splice(0,0,element);
}

//尾部出队，就是删除数组的最后一个元素
function dequeueBack(){
    return this.dataStore.splice(this.dataStore.length-1, 1);
}

//出队，就是删除数组的第一个元素
function dequeueFront(){
    return this.dataStore.shift();
}

//取出数组的第一个元素
function front(){
    return this.dataStore[0];
}
//取出数组的最后一个元素
function back(){
    return this.dataStore[this.dataStore.length-1];
}

function toString(){
    var retStr = "";
    for (var i=0; i<this.dataStore.length; ++i) {
        retStr += this.dataStore[i] + "&nbsp;"
    }
    return retStr;
}
//判断数组是否为空
function empty(){
    if(this.dataStore.length == 0){
        return true;
    }else{
        return false;
    }    
}
//返回数组中元素的个数
function count(){
    return this.dataStore.length;
}

var q = new Queue();
q.enqueueFront("1");
q.enqueueFront("2");
q.enqueueBack("3");
q.enqueueBack("4");
document.write(q.toString());
document.write(‘<br>‘);

q.dequeueFront();
document.write(q.toString());
document.write(‘<br>‘);

q.dequeueBack();
document.write(q.toString());
document.write(‘<br>‘);
document.write(‘<br>‘);

/*---------------------------判断字符串是否是回文-------------------------*/
function isPalindrome(str){
    var queue = new Queue();
    for (var i=0; i<str.length; i++) {
        queue.enqueueFront(str[i]);
    }
    
    var newStr = "";
    while (!queue.empty()){
        newStr += queue.dequeueFront();
    }
    
    document.write(newStr);
    document.write(‘<br>‘);
    if(str == newStr){
        document.writeln(str + " 是回文");
    }else{
        document.writeln(str + " 不是回文");
    }
}

isPalindrome("racecar");
document.write(‘<br>‘);
isPalindrome("helloword");