队列的JS实现

队列和栈相似，都是对插入和删除操作的部位做了限制特殊的线性表。在队列中，只能从一头删除节点，这一头叫做队首；而另一端只能做插入操作，这一头叫做队尾。很容易理解，队列是一个“先进先出”的线性表。队列的应用有一个很常见的例子，就是打印机的作业队列，打印机会维护一个作业队列，先入队的作业先执行~

同样的，根据存储结构的不同，队列也有顺序队列和链式队列两种实现，代码如下：

function LinkedQueue () {
        //节点结构定义
	var Node = function(element){
		this.element = element;
		this.next = null;
	} 

	var length = 0,
		front,//队首指针
		rear;//队尾指针
        //入队操作
	this.push = function(element){
		var node = new Node(element),
			current;

		if(length == 0){
			front = node;
			rear = node;
			length++;

			return true;
		}else{
			current = rear;
			current.next = node;
			rear = node;
			length++;

			return true;
		}
	}
        //出队操作
	this.pop = function(){
		if(!front){
			return 'Queue is null';
		}else{
			var current = front;
			front = current.next;
			current.next = null;
			length--;
			return current;
		}
	}
        //获取队长
	this.size = function(){
		return length;
	}
        //获取队首
	this.getFront = function(){
		return front;
	}
        //获取队尾
	this.getRear = function(){
		return rear;
	}

	this.toString = function(){
		var str = '',
			current = front;

		while(current){
			str += current.element;
			current = current.next;
		}

		return str;
	}
        //清除队列
	this.clear = function(){
		front = null;
		rear = null;
		length = 0;
		return true;
	}
}

function ArrayQueue(){
	var arr = [];
        //入队操作
	this.push = function(element){
		arr.push(element);
		return true;
	}
        //出队操作
	this.pop = function(){
		return arr.shift();
	}
        //获取队首
	this.getFront = function(){
		return arr[0];
	}
        //获取队尾
	this.getRear = function(){
		return arr[arr.length - 1]
	}
        //清空队列
	this.clear = function(){
		arr = [];
	}
        //获取队长
	this.size = function(){
		return length;
	}
}