Linked Lists

LinkedList.js

class LinkedList {
	constructor() {
		this.head = null;
	}
	
	insertFirst(data) {
		this.head = new Node(data, this.head);
	}
	
	size() {
		let counter = 0;
		let node = this.head;
		
		while(node) {
			counter++;
			node = node.next;
		}
		
		return counter;
	}
	
	getFirst() {
		return this.head;
	}
	
	getLast() {
		if (!this.head) {
			return null;
		}
		
		let node = this.head;
		
		while(node) {
			if (!node.next) {
				return node;
			}
			
			node = node.next;
		}
	}
	
	clear() {
		this.head = null;
	}
	
	removeFirst() {
		if (this.head) {
			this.head = this.head.next;
		}
		
		// this.removeAt(0);
	}
	
	removeLast() {
		if (!this.head) {
			return null;
		}
		
		if (!this.head.next) {
			this.head = null;
			return;
		}
		
		let node = this.head.next;
		let previousNode = this.head;
		
		while(node.next) {
			previousNode = node;
			node = node.next;
		}
		
		previousNode.next = null;
	}
	
	insertLast(data) {		
		const lastNode = this.getLast();
		
		if (lastNode) {
			lastNode.next = new Node(data);
		}  else {
			this.head = new Node(data);
		}
	}
	
	getAt(index) {		
		let counter = 0;
		let node = this.head;
		
		while(node) {
			if (counter === index) {
				return node;
			}
			
			counter++;
			node = node.next;
		}
		
		return null;
	}
	
	removeAt(index) {
		if (!this.head) {
			return;
		}
		
		if (index === 0) {
			this.head = this.head.next;
			return;
		}
		
		const previousNode = this.getAt(index - 1);
		
		if (!previousNode || !previousNode.next) {
			return;
		}
		
		previousNode.next = previousNode.next.next;
	}
	
	insertAt(data, index) {	
		if (!this.head) {
			this.head = new Node(data);
			return;
		}
		
		if (index === 0) {
			this.head = new Node(data, this.head);
			return;
		}
	
		const previousNode = this.getAt(index - 1) || this.getLast();
		previousNode.next = new Node(data, previousNode.next);
	}
	
	forEach(fn) {
		let node = this.head;
		let counter = 0;
		
		while (node) {
			fn(node, counter);
			node = node.next;
			counter++;
		}
	}
	
	*[Symbol.iterator]() {
		let node = this.head;
		
		while (node) {
			yield node;
			node = node.next;
		}
	}
}

Node.js

class Node {
	constructor(data, next = null) {
    	this.data = data;
		this.next = next;
	}
}