Linked List in TypeScript.

interface Node<T> {
    prev: Node<T>,
    value: T,
    next: Node<T>,
}


export default class LinkedList<T> {
    private _head: Node<T>;
    private _tail: Node<T>;

    constructor() {
        this._head = null;
        this._tail = null;
    }

    addToHead(value: T): void {
        const newNode: Node<T> = {
            prev: null,
            value: value,
            next: this._head,
        };

        // Linked list has already been initialized
        if (this._head) this._head.prev = newNode;
        // Linked list has not been initialized yet
        else this._tail = newNode;

        this._head = newNode;
    }

    addToTail(value: T): void {
        const newNode: Node<T> = {
            prev: this._tail,
            value: value,
            next: null,
        };

        // Linked list has already been initialized
        if (this._tail) this._tail.next = newNode;
        // Linked list has not been initialized yet
        else this._head = newNode;

        this._tail = newNode;
    }

    removeHead(): T {
        if (!this._head) return null;

        const value = this._head.value;
        this._head = this._head.next;

        // Linked list has at least one node
        if (this._head) this._head.prev = null;
        // Linked list is empty
        else this._tail = null;

        return value;
    }

    removeTail(): T {
        if (!this._tail) return null;

        const value = this._tail.value;
        this._tail = this._tail.prev;

        // Linked list has at leaast one node
        if (this._tail) this._tail.next = null;
        // Linked list is empty
        else this._head = null;

        return value;
    }

    search(value: T): boolean {
        for (let pointer: Node<T> = this._head; pointer; pointer = pointer.next)
            if (pointer.value === value) return true;

        return false;
    }

    indexOf(value: T): Array<number> {
        const indices: Array<number> = [];

        for (let pointer: Node<T> = this._head, i: number = 0; pointer; pointer = pointer.next, i++)
            if (pointer.value === value) indices.push(i);

        return indices;
    }
}