Single Linked List Implementation in JavaScript

mySinglyLinkedList.js

// Creating node
class Node {
	constructor(value) {
		this.value = value;
		this.next = null;
	}
}

class LinkedList {
	// Empty Linked List will not be formed.
	constructor(value) {
		this.head = {
			value: value,
			next: null
		};
		this.tail = this.head;
		this.length = 1;
	}
	
	// Print the list
	printList() {
		let list = [];
		let currentNode = this.head;
		while (currentNode !== null) {
			list.push(currentNode.value);
			currentNode = currentNode.next;
		}

		console.log(list.join(' --> '));
	}

	// Append a value at the end
	append(value) {
		let newNode = new Node(value);
		this.tail.next = newNode;
		this.tail = newNode;

		this.length++;
		this.printList();
		return this.length;
	}

	// Append a value at the beginning
	prepend(value) {
		let newNode = new Node(value);
		newNode.next = this.head;
		this.head = newNode;

		this.length++;
		this.printList();
		return this.length;
	}

	// Insert a node at a given index
	insert(index, value) {
		// Verify index
		if (!Number.isInteger(index) || index < 0 || index > this.length + 1) {
			console.log(`Enter valid index. Current length of the linked list is ${this.length}`);
			return this.length;
		}
		
		// Insert at index 0 = prepend
		if (index === 0) {
			this.prepend(value);
			return this.length;
		}

		// Insert at the end = append
		if (index === this.length) {
			this.append(value);
			return this.length;
		}

		// Insert at given index
		let newNode = new Node(value);
		let previousNode = this.head;
		for (let k = 0; k < index - 1; k++) {
			previousNode = previousNode.next;
		}
		let nextNode = previousNode.next;
		newNode.next = nextNode;
		previousNode.next = newNode;

		this.length++;
		this.printList();
		return this.length;
	}

	// Remove a node at given index
	remove(index) {
		// Verify index
		if (!Number.isInteger(index) || index < 0 || index >= this.length) {
			console.log(`Enter valid index. Current length of the linked list is ${this.length}`);
			return this.length;
		}

		// Remove head node
		if (index === 0) {
			this.head = this.head.next;
			this.length--;
			this.printList();
			return this.length;
		}

		// Remove tail node
		if (index === this.length - 1) {
			let lastNode = this.head.next;
			let secondLastNode = this.head;

			while (lastNode.next !== null) {
				secondLastNode = secondLastNode.next;
				lastNode = lastNode.next;
			}

			secondLastNode.next = null;
			this.tail = this.secondLastNode;

			this.length--;
			this.printList();
			return this.length;
		}

		// Remove at given index
		let previousNode = this.head;
		for (let k = 0; k < index - 1; k++) {
			previousNode = previousNode.next;
		}
		let nextNode = previousNode.next;
		previousNode.next = nextNode.next;

		this.length--;
		this.printList();
		return this.length;
	}
}

const myLinkedList = new LinkedList(10);
myLinkedList.printList();                   // 10

myLinkedList.append(5);                     // 10 --> 5
myLinkedList.append(16);                    // 10 --> 5 --> 16

myLinkedList.prepend(1);                    // 1 --> 10 --> 5 --> 16

// Insert 99 at index 2
myLinkedList.insert(2, 99);                 // 1 --> 10 --> 99 --> 5 --> 16
myLinkedList.insert(20, 88);                // Enter valid index. Current length of the linked list is 5.
myLinkedList.insert(5, 80);                 // 1 --> 10 --> 99 --> 5 --> 16 --> 80
myLinkedList.insert(0, 80);                 // 80 --> 1 --> 10 --> 99 --> 5 --> 16 --> 80

myLinkedList.remove(0);                     // 1 --> 10 --> 99 --> 5 --> 16 --> 80
myLinkedList.remove(5);                     // 1 --> 10 --> 99 --> 5 --> 16
myLinkedList.remove(2);                     // 1 --> 10 --> 5 --> 16