linkedList.js

'use strict';

var head = null; // head of linked list

function addNode(val) {
	
	var node = {
		val: val,
		next: null
	}
	
	if (head == null) {
		head = node;
	} else {
		var lastNode = getLastNode();
		lastNode.next = node;
	}
	
}

function popNode() {
	
	if (head == null) {
		console.log("list is empty");
		return null;
	}
	
	var pop = null;
	
	if (head.next == null) {
		pop = head;
		head = null;
		return pop;
	}
	
	var walker = head;
	
	while (walker.next != null) {
		if (walker.next.next == null) {
			pop = walker.next;
			walker.next = null;
		} else {
			walker = walker.next;			
		}
		
	}
	
	return pop;
	
}

function getLastNode() {
	
	if (head == null) {
		console.log("list is empty");
		return null;
	}
	
	var walker = head;
	
	while (walker.next != null) {
		walker = walker.next;
	}
	
	return walker;
	
}

function printList() {
	
	if (head == null) {
		console.log("list is empty");
		return null;
	}
	
	var walker = head;
	
	while (walker.next != null) {
		console.log(walker.val);
		walker = walker.next;
	}
	
	console.log(walker.val);
	
}

function getNodeAtPosition(position) {
	
	if (head == null) {
		console.log("list is empty");
		return null;
	}
	
	var walker = head;
	
	for (var i = 0; i < position; i += 1) {
		
		if (walker.next != null) {
			walker = walker.next;
		} else {
			console.log("List isn't " + position + " positions long." );
			return null;
		}
				
	}
	
	return walker;
	
}

function addNodeAtPosition(val, position) {
	
	var node = {
		val: val,
		next: null
	}
	
	var walker = head;
		
	if (position == 0) {
		
		node.next = walker;
		head = node;	
	
	} else {
	
		for (var i = 0; i < (position - 1); i += 1) {
				
			if (walker.next != null) {
				walker = walker.next;
			} else {
				console.log("List isn't " + position + " positions long." );
				return null;
			}
					
		}
	
		node.next = walker.next;
			
		walker.next = node;			
		
	}

	
}

function removeNodeAtPosition(position) {
	
	var walker = head;
		
	if (position == 0) {
		
		head = head.next;
	
	} else {
		
		var prevNode = getNodeAtPosition(position - 1);
		var nextNode = getNodeAtPosition(position + 1);
		
		if (nextNode) {
			prevNode.next = nextNode;
		} else {
			prevNode.next = null;
		}
		
	}
	
}

function reverseList() {
	
	var tempHead = popNode();
	var walker = tempHead;
	var prevNode = popNode();
	
	while (prevNode != null) {
		walker.next = prevNode;
		walker = prevNode;
		prevNode = popNode();
	}
	
	head = tempHead;
	
}


// var test add node and last node
head = { val: "1", next: { val: "2", next: { val: "3", next: null } } };
addNode('4');
//console.log(head);
printList();

// test find position
console.log(getNodeAtPosition(2));
console.log(getNodeAtPosition(4));

// test add node at position
addNodeAtPosition('2a', 2);
addNodeAtPosition('0', 0);
printList();

// test removeNodeAtPosition
removeNodeAtPosition(0);
printList();

removeNodeAtPosition(2);
removeNodeAtPosition(3);
printList();

// test popNode
console.log(popNode());
console.log(popNode());
console.log(popNode());
printList();

// test reverseList
addNode('1');
addNode('2');
addNode('3');
addNode('4');
addNode('5');
addNode('6');
reverseList();
printList();