A singly linked list you can reverse

A linked list stores each value in a node that points at the next one. Nothing needs to shift when you insert at the head, which is why lists show up inside schedulers, undo chains and the internals of frameworks.

Implement a LinkedList class. It is constructed with no arguments and starts empty. append(value) adds a value at the tail and returns the new length. prepend(value) adds a value at the head and returns the new length. get(index) returns the value at a zero-based index, or undefined when the index is negative or past the end. removeAt(index) removes the node at that index and returns its value, or returns undefined when the index is out of range. size() returns the number of values. toArray() returns the values as a plain array from head to tail, and [] when empty. reverse() reverses the list in place; its return value is not used.

const l = new LinkedList();
l.append("x"); // 1
l.append("y"); // 2
l.prepend("a"); // 3
l.toArray();   // ["a", "x", "y"]

const l = new LinkedList();
[1, 2, 3].forEach((v) => l.append(v));
l.removeAt(1); // 2 — removes the middle
l.toArray();   // [1, 3]
l.reverse();
l.toArray();   // [3, 1]