Reverse a Linked List, because why not.

0.reverseList.js

function buildList(values) {
  return values.reduceRight((next, value) => ({ value, next }), null);
}

function getValues(node) {
  const values = [];
  while (node) {
    values.push(node.value);
    node = node.next;
  }
  return values;
}

function reverseList(list) {
  let source = list;
  let target = null;
  while (source !== null) {
    const node = source;
    source = node.next;
    node.next = target;
    target = node;
  }
  return target;
}

1.usage.js

const list = buildList([1, 2, 3]);
// {
//   "value": 1,
//   "next": {
//     "value": 2,
//     "next": {
//       "value": 3,
//       "next": null
//     }
//   }
// }

const reverse = reverseList(list);
// {
//   "value": 3,
//   "next": {
//     "value": 2,
//     "next": {
//       "value": 1,
//       "next": null
//     }
//   }
// }

const values = getValues(reverse);
// [3, 2, 1]