1class Node {
2    constructor(val) {
3        this.val = val;
4        this.next = null;
5    }
6}
7
8class MyLinkedList {
9    constructor() {
10        this.head = null;
11    }
12
13    get(index) {
14        let current = this.head;
15        for (let i = 0; i < index; i++) {
16            if (!current) return -1;
17            current = current.next;
18        }
19        return current ? current.val : -1;
20    }
21
22    addAtHead(val) {
23        const node = new Node(val);
24        node.next = this.head;
25        this.head = node;
26    }
27
28    addAtTail(val) {
29        const node = new Node(val);
30        if (!this.head) {
31            this.head = node;
32            return;
33        }
34        let current = this.head;
35        while (current.next) {
36            current = current.next;
37        }
38        current.next = node;
39    }
40
41    addAtIndex(index, val) {
42        if (index === 0) {
43            this.addAtHead(val);
44            return;
45        }
46        let current = this.head;
47        for (let i = 0; i < index - 1; i++) {
48            if (!current) return;
49            current = current.next;
50        }
51        if (current) {
52            const node = new Node(val);
53            node.next = current.next;
54            current.next = node;
55        }
56    }
57
58    deleteAtIndex(index) {
59        if (index === 0 && this.head) {
60            this.head = this.head.next;
61            return;
62        }
63        let current = this.head;
64        for (let i = 0; i < index - 1 && current; i++) {
65            current = current.next;
66        }
67        if (current && current.next) {
68            current.next = current.next.next;
69        }
70    }
71}

1