multiMap

Reactively maps items from a source proxy (array or object) to a target proxied object, where each source item can contribute multiple key-value pairs to the target.

It iterates over the target proxy. For each item, it calls func.

• If func returns an object, all key-value pairs from that object are added to the result proxy.
• If func returns undefined, the item contributes nothing.

The returned proxy automatically updates when:

• Items are added/removed/updated in the target proxy.
• Any proxied data read within the func call changes (for a specific item).
• If multiple input items produce the same output key, the last one processed usually “wins”, but the exact behavior on collision depends on update timing.

This is useful for “flattening” or “indexing” data, or converting an observable array to an observable object.

Param

source

The source proxied array or object.

Param

func

A function (value, key) => ({...pairs} | undefined) that transforms an item into an object of key-value pairs to add, or undefined to add nothing.

Template

IN

The type of items in the source proxy.

Template

OUT

The type of the aggregated output object (should encompass all possible key-value pairs).

Example

Creating an index from an array

const $items = A.proxy([
  { id: 'a', value: 10 },
  { id: 'b', value: 20 },
]);
const $itemsById = A.multiMap($items, ($item) => ({
  [$item.id]: $item.value,
  [$item.id+$item.id]: $item.value*10,
}));
// $itemsById is proxy({ a: 10, aa: 100, b: 20, bb: 200 })

A(() => console.log($itemsById));

$items.push({ id: 'c', value: 30 });
// $itemsById becomes proxy({ a: 10, aa: 100, b: 20, bb: 200, c: 30, cc: 300 })

Call Signature

multiMap<IN, OUT>(source, func): OUT

Defined in: aberdeen.ts:3355

When using an array as source.

Type Parameters

IN

IN

OUT

OUT extends object

Parameters

source

IN[]

func

(value, index) => OUT

Returns

OUT

Call Signature

multiMap<K, IN, OUT>(source, func): OUT

Defined in: aberdeen.ts:3360

When using an object as source.

Type Parameters

K

K extends string | number | symbol

IN

IN

OUT

OUT extends object

Parameters

source

Record<K, IN>

func

(value, index) => OUT

Returns

OUT

Call Signature

multiMap<K, IN, OUT>(source, func): OUT

Defined in: aberdeen.ts:3366

When using a Map as source.

Type Parameters

K

K

IN

IN

OUT

OUT extends object

Parameters

source

Map<K, IN>

func

(value, key) => OUT

Returns

OUT