var Queue = module.exports = function () {

this.head = null;

this.tail = null;

this.length = 0;

};

Queue.prototype.enqueue = function (value) {

var node = {

value: value,

next: null

};

// If there is currently no head node, set it to the current node.

if (!this.head) {

this.head = node;

}

// If we have a tail node already, set it's next property to be the current

// node.

if (this.tail) {

this.tail.next = node;

}

// Update the tail to be the next node.

this.tail = node;

return this.length += 1;

};

Queue.prototype.dequeue = function () {

if (!this.head) { return; }

var node = this.head;

// Update the head reference and remove the next node reference from the

// previous head.

this.head = node.next;

node.next = null;

// Remove the tail node if we have no more head node.

if (!this.head) { this.tail = null; }

this.length -= 1;

return node.value;

};