Queues

class MyLinkedList {
    constructor(value) {
        if(value === undefined) {
            this.head = null;
            this.length = 0;
        }else {
            this.head = {
                value,
                next: null
            }
            this.length = 1;
        }
        this.tail = this.head;
    }
    newNode(value) {
        return {
            value,
            next: null
        };
    }
    append(value) {
        const node = this.newNode(value);
        if(this.tail === null) {
            this.tail = node;
            this.head = this.tail;
        }else {
            this.tail.next = node;
            this.tail = this.tail.next;
        }
        this.length++;
        return this;
    }
    prepend(value) {
        const node = this.newNode(value);
        if(this.head === null) {
            this.head = node;
            this.tail = this.head;
        }else {
            node.next = this.head;
            this.head = node;
        }
        this.length++;
        return this;
    }
    insertNode(value, index) {
        if(index >= this.length) {
            return this.append(value);
        }else if(index <= 0) {
            return this.prepend(value);
        }else {
            const node = this.newNode(value);
            const prevNode = this.traversal(index-1);
            const nextNode = prevNode.next;
            prevNode.next = node;
            node.next = nextNode;
            this.length++;
            return this;
        }
    }
    deleteNode(index) {
        if(this.length === 0 || index < 0 || index >= this.length) {
            return false;
        }else {
            if(index === 0) {
                if(this.length === 1) {
                    this.head = null;
                    this.tail = null;
                    this.length = 0;
                }else {
                    this.head = this.head.next;
                    this.length--;
                }
            }else {
                const prevNode = this.traversal(index-1);
                const nextNode = prevNode.next;
                prevNode.next = nextNode.next;
                nextNode.next = null;
                this.length--;
                if(nextNode === this.tail) {
                    this.tail = prevNode;
                }
            }
            return true;
        }
    }
    reverse() {
        if(this.length <= 1) {
            return this;
        }
        let prevNode = null, curNode = this.head;
        while(curNode !== null) {
            const temp = curNode.next;
            curNode.next = prevNode;
            prevNode = curNode;
            curNode = temp;
        }
        this.tail = this.head;
        this.head = prevNode;
        return this;
    }
    traversal(index) {
        let current = this.head;
        for(let i=0;i < index && current !== null;i++) {
            current = current.next;
        }
        return current;
    }
}

class Queues {
    constructor() {
        this.data = new MyLinkedList();
    }
    enque(value) {
        return this.data.append(value);
    }
    dequeue() {
        const val = this.data.head ? this.data.head.value : null;
        if(typeof val !== "undefined") {
            this.data.deleteNode(0);
        }
        return val;
    }
    peak() {
        return this.data.head ? this.data.head.value : null;
    }
}