singlyLinkedLists.js

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

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

    traversy() {
        let current = this.head
        while(current) {
            console.log(current.val)
            current = current.next;
        }
    }

    print() {
        let arr = [];
        let current = this.head;
        while (current) {
            arr.push(current.val)
            current = current.next
        }
        console.log(arr)
    }

    push(val) {
        let 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 = currentHead.next;
        this.length--;
        if (this.length === 0) {
           this.tail = null; 
        }
        return currentHead;
    }

    unshift(val) {
        let newNode = new Node(val);
        if (!this.head) {
            this.head = newNode;
            this.tail = this.head;
        } else {
            newNode.next = this.head;
            this.head = newNode;
        }
        this.length ++;
        return this;
    }

    get(index) {
        if (index < 0 || index >= this.length) return null;
        let counter = 0;
        let current = this.head;
        while (counter !== index) {
            current = current.next;
            counter++;
        }
        return current
    }

    set(index, val) {
        let target = this.get(index)
        if (target ) {
            target.val = val;
        }
        return this;
    }

    insert(index, val) {
        if (index < 0 || index > this.length) return false;
        if (index === 0) return !!this.unshift(val);
        if (index === this.length) return !!this.push(val);
        
        let newNode = new Node(val);
        let prev = this.get(index - 1);
        let next = prev.next;
        prev.next = newNode;
        newNode.next = next;
        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();
        
        let prev = this.get(index - 1);
        let removed = prev.next;
        prev.next = removed.next;
        this.length--;
        return removed
    }

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

        let next = null;
        let prev = null;
        for (let i = 0; i < this.length; i++) {
            next = node.next;
            node.next = prev;
            prev = node;
            node = next
        }
        return this;
    }
}

let list = new SinglyLinkedList()