class Node {
    constructor(data, next) {
        this.data = data;
        this.next = next;
    }
}

function createListFromArray(array) {
    let list = null;
    for (const item of array) {
        list = new Node(item, list);
    }
    return list;
}

function displayList(list) {
    while (list) {
        console.log(list.data);
        list = list.next;
    }
}

function insertNth(head, index, data) {
    if (index === 0) {
        return new Node(data, head);
    } else if (head && index > 0) {
        head.next = insertNth(head.next, index - 1, data);
        return head;
    } else {
        throw Error("Out of bounds exception");
    }
}

let array = [4,2,1];
let list = createListFromArray(array);
list = insertNth(list, 2, 3);
displayList(list);