Singly Linked Lists

singly-linked-lists.js

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


class SinglyLinkedList {
    constructor() {
        this.head = null;
        this.tail = null;
        this.length = 0;
    }
    push(val) {
        const newNode = new Node(val);


        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 undefined;


        let current = this.head;
        let newTail = current;

        while (current.next) {
            newTail = current;
            current = current.next;
        }

        this.tail = newTail;
        this.tail.next = null;
        this.length--;

        if (this.length == 0) {
            this.head = null;
            this.tail = null;
        }

        return current;
    }
    shift() {
        if (!this.head) return undefined;

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

        if (this.length == 0) {
            this.tail = null;
        }

        return currentHead;
    }
    unshift(val) {

        const newNode = new Node(val);

        if (this.head) {

            newNode.next = this.head;

        } else {
            this.tail = newNode;
        }

        this.head = newNode;
        this.length++;

        return this;
    }
    get(index) {

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

        let count = 0;
        let current = this.head;


        while (count < index) {

            current = current.next;
            count++;

        }

        return current;

    }
    set(index, val) {

        const node = this.get(index)

        if (node) {
            node.val = val
            return true;
        }
        return false;

    }
    insert(index, val) {
        if (index < 0 || index > this.length) return false;
        if (index == this.length) return !!this.push(val);
        if (index == 0) return !!this.unshift(val);


        const newNode = new Node(val);
        const prev = this.get(index - 1);
        const temp = prev.next;
        prev.next = newNode;
        newNode.next = temp;
        this.length++;

        return true;
    }
    remove(index) {
        if (index < 0 || index >= this.length) return undefined;
        if (index == this.length - 1) return !!this.pop();
        if (index == 0) return !!this.shift();

        const prevNode = this.get(index - 1);
        const current = prevNode.next;
        prevNode.next = current.next;

        this.length--;

        return current;
    }
    reverse() {
        let node = { ...this.head };
        let next;
        let previous = null;

        while (node) {
            next = node.next;
            node.next = previous;
            previous = node;
            node = next;
        }

        return previous
    }
}

const list = new SinglyLinkedList();

list.push("hi");
list.push("how");
list.push("are");
list.push("you");
list.push("today");