Files
ponytail/examples/group-by.md
Jesus cornelio b345e49385 examples: add 6 new over-engineering survivors + platform-native guide (#109)
New examples (examples/):
- modal-dialog: <dialog> vs Radix/react-modal
- url-params: URLSearchParams vs query-string
- number-formatting: Intl.NumberFormat vs numeral
- infinite-scroll: IntersectionObserver vs react-infinite-scroll-component
- deep-clone: structuredClone vs lodash.cloneDeep / JSON hack
- group-by: Object.groupBy vs lodash.groupBy

New doc (docs/platform-native.md):
Comprehensive reference of platform-native solutions across HTML elements,
CSS, Browser APIs, Node.js stdlib, Python stdlib, and database features.
Covers 60+ cases where the platform already has what developers reach for
a package to do.
2026-06-19 00:24:29 +02:00

940 B

Group By

Task: "Group this array of objects by a key."

Without Ponytail

npm install lodash
import { groupBy } from "lodash";

const byStatus = groupBy(orders, "status");
// → { pending: [...], shipped: [...], delivered: [...] }

Or the hand-rolled version:

const byStatus = orders.reduce((acc, order) => {
  (acc[order.status] ??= []).push(order);
  return acc;
}, {});

With Ponytail

// ponytail: Object.groupBy does this
const byStatus = Object.groupBy(orders, order => order.status);
// → { pending: [...], shipped: [...], delivered: [...] }

1 dependency (or a reduce) → 1 built-in. Object.groupBy shipped in Chrome 117, Firefox 119, Safari 17.4, Node.js 21. If you need a Map instead of a plain object: Map.groupBy(orders, o => o.status). Check your target runtime; if you need IE11 or old Node, the reduce one-liner is still the right call — not lodash.