JavaScript (ES2026) reference · Object Methods

JavaScript Object.groupBy() Method

Group the items of an iterable into an object whose keys come from a callback, e.g. orders grouped by status.

JavaScript (ES2026) Since ES2024

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Syntax

Object.groupBy(items, callbackFn)

Parameters

Parameter	Description
`items`	An iterable, such as an array.
`callbackFn`	Returns the group key for `(item, index)`.

Return value

A null-prototype object of arrays.

Examples

Group by a fieldTry it yourself

const orders = [{ id: 1, status: "paid" }, { id: 2, status: "open" }, { id: 3, status: "paid" }];
const byStatus = Object.groupBy(orders, (o) => o.status);
console.log(byStatus.paid.map((o) => o.id), byStatus.open.length);

Output

[ 1, 3 ] 1

Group by a computed keyTry it yourself

const nums = [1, 2, 3, 4, 5, 6];
console.log(Object.groupBy(nums, (n) => (n % 2 ? "odd" : "even")));