Singly Linked List

sll.js

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

class singlyLinkedList {
    constructor() {
        this.length = 0;
        this.head = null;
        this.tail = null;
    }

    push(value) {
        const newNode = new Node(value);
        
        if (!this.head) {
            this.head = newNode;
            this.tail = this.head;
        } else {
            this.tail.next = newNode;
            this.tail = newNode;
            
        }

        this.length++;

        return this;
    }

    pop() {
        if (!this.head) return;

        let current = this.head;

        if (this.length === 1) {
            this.head = null;
            this.tail = null;

            this.length--;

            return current;
        }

        let temp = current;

        while (current && current.next) {
            temp = current;
            current = current.next;
        }

        this.tail = temp;
        this.tail.next = null;

        this.length--;

        return temp;
    }

    shift() {
        if (!this.head) return;

        let currentHead = this.head;
        this.head = currentHead.next;

        this.length--;

        if (this.length <= 0) this.tail = null;

        return currentHead;
    }

    unshift(value) {
        const node = new Node(value);
        const currentHead = this.head;
        
        if (!currentHead) {
            this.head = node;
            this.tail = this.head;
        } else {
            node.next = currentHead;
            this.head = node;
        }

        this.length++;

        return this;
    }

    get(index) {
        if (index < 0 || index >= this.length) return;

        let currentNodeIndex = 0;
        let currentNode = this.head;

        while (currentNodeIndex < index) {
            currentNode = currentNode.next;
            currentNodeIndex++
        }

        return currentNode;
    }

    set(value, index) {
        const node = this.get(index);

        if (!node) return false; // throw new Error('Invalid index');

        node.value = value;

        return true;
    }

    insert(value, index) {
        if (index < 0 || index > this.length) return false;

        if (index === 0) {
            return !!this.unshift(value);
        }

        if (index === this.length) {
            return !!this.push(value);
        }

        const previousNode = this.get(index - 1);
        const newNode = new Node(value);
        
        newNode.next = previousNode.next;
        previousNode.next = newNode; 

        this.length++;

        return true;
    }

    remove(index) {
        if (index < 0 || index >= this.length) return;

        if (index === 0) return this.shift();

        if (index === this.length - 1) return this.pop();

        const previousNode = this.get(index - 1);
        const removed = previousNode.next;
        
        previousNode.next = removed.next;

        this.length--;

        return removed;
    }

    print() {
        const array = [];
        let current = this.head;

        while(current) {
            array.push(current.value);
            current = current.next;
        }

        // const array = Array.from({ length: this.length }).map(() => {
        //     const val = current.value;
        //     current = current.next;
        //     return val;
        // });

        console.log(array);
    }

    reverse() {
        let currentNode = this.head;
        this.head = this.tail;
        this.tail = currentNode;

        let next, prev = null;

        // for (let i = 0; i < this.length; i++) {
        while (currentNode) {
            next = currentNode.next;
            currentNode.next = prev;
            prev = currentNode;
            currentNode = next
        }

        return this;
    }
}

const list = new singlyLinkedList();

list.push('Hey there!')
list.push('Sup')
list.push('Im alright')
list.push('Whatever!')

// list.pop();
// list.shift();
// list.unshift('Chairman')

// console.log(list);
// console.log(list.get(4))

// list.set('Chairwoman', 1);
// console.log(list)

// list.insert('New item', 12);

// console.log(list)
// list.remove(2);
// console.log(list)

list.print();
list.reverse();
list.print();