ES2024 New Features: What's Coming in JavaScript

Tue, 12 Mar 2024 00:00:00 +0900

ECMAScript 2024 (ES15) introduces several long-anticipated features to JavaScript. This article covers the new capabilities with practical examples and guidance on adoption timelines.

Array Grouping: Object.groupBy and Map.groupBy

One of the most requested JavaScript features has finally arrived. Object.groupBy and Map.groupBy partition array elements into groups based on a callback:

const inventory = [
 { name: "asparagus", type: "vegetables", quantity: 5 },
 { name: "bananas", type: "fruit", quantity: 0 },
 { name: "goat", type: "meat", quantity: 23 },
];

const byType = Object.groupBy(inventory, ({ type }) => type);
// { vegetables: [{ name: "asparagus", ... }],
// fruit: [{ name: "bananas", ... }],
// meat: [{ name: "goat", ... }] }

Map.groupBy preserves non-string keys, making it ideal for grouping by objects or symbols. This eliminates the need for external libraries or manual reduce patterns.

Es2024 on Commentary of Takao

ES2024 New Features: What's Coming in JavaScript

Array Grouping: Object.groupBy and Map.groupBy