Array grouping

Category: JavaScript
Type: Chromium catches up
Status: Enabled by default (Chrome 117)
Intent stage: Prepare to ship

Breaking change: No
Enterprise impact: None
Chromium flag: --harmony-array-grouping
Spec maturity: Working draft
Web Platform Tests: No

WPT details: In test262. https://github.com/tc39/test262/tree/main/test/built-ins/Object/prototype/groupBy https://github.com/tc39/test262/tree/main/test/built-ins/Map/prototype/groupBy

Summary

Adds news Object.groupBy(iterable, groupCallback) and Map.groupBy(iterable, groupCallback) to perform a grouping or bucketing operation. The Object method returns a plain object, where the groups are property keys. The Map method returns a Map, where the keys can be arbitrary values.

Motivation

From the proposal explainer: Array grouping is an extremely common operation, best exemplified by SQL's GROUP BY clause and MapReduce programming (which is better thought of map-group-reduce). The ability to combine like data into groups allows developers to compute higher order datasets, like the average age of a cohort or daily LCP values for a webpage.

Standards & signals

Specification: https://tc39.es/proposal-array-grouping
Firefox: Shipped/Shipping
Safari: Shipped/Shipping
Web developers: Strongly positive
Tracking bug: https://bugs.chromium.org/p/v8/issues/detail?id=12499

Ecosystem

Web Platform Tests: https://wpt.fyi/results/?q=test%2Fbuilt-ins%2FObject%2Fprototype%2FgroupBy
Chrome Platform Showcase: https://chrome-platform-showcase.paulkinlan-ea.deno.net/features
GenDN reference: https://gendn.paulkinlan-ea.deno.net/features
chrome.dev demos search: https://www.google.com/search?q=site%3Achrome.dev+Array%20grouping
MDN Web Docs: https://developer.mozilla.org/en-US/search?q=Array%20grouping
Baseline status: https://webstatus.dev/?q=Array%20grouping

Explainers: https://github.com/tc39/proposal-array-grouping/blob/main/README.md

View on chromestatus.com