newQueueClass.js

function Queue() {
  this.tail = null;
	this.head = null;
}
Queue.prototype.enqueue = function(n) {
	if(this.head == null){
		this.head = n;
		this.tail = n;
	}
	else{
		this.tail.setNextNode(n);
		this.tail = this.tail.getNextNode();
	}
}
Queue.prototype.dequeue = function() {
	
	if(this.tail != null){
		this.head = this.head.getNextNode();
		return this.head;
	}
}
Queue.prototype.peek = function(n) {
	return this.head;
}
Queue.prototype.getLength = function() {
	
	if(this.head == null){
		return 0;
	}
	else{
		var counter = 1;
		while(this.head.getNextNode() != null){
			counter++;
			this.head = this.head.getNextNode();
		}
		return counter;
	}
}

#19: This line is problematic: since we have just updated the value of this.head in the previous line, we have lost access to the node that we are trying to return