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# Use infused data

> Merge an array of Replyke entities with data fetched from your own backend

## Overview

`useInfusedData` takes an array of entities and an optional `infuseData` function, and returns an array of those entities merged with external data under an `infusion` key. Results are cached by `foreignId` per hook instance.

This hook is used internally by `useEntityList` when you pass `infuseData`. Use it directly only if you need to infuse a custom entity array that isn't managed by `useEntityList`.

See [Infusing Data](/sdk/entity-lists/infuse-data) for a full guide.

## Props

<ParamField path="entities" type="Entity[]" required>
  The entities to infuse.
</ParamField>

<ParamField path="infuseData" type="(foreignId: string) => Promise<Record<string, any> | null>">
  Called once per unique `foreignId`. Return `null` if the external record is not found.
</ParamField>

## Returns

`(Entity & { infusion: Record<string, any> })[]`

Each item in the returned array is the original entity with an added `infusion` property containing the data returned by `infuseData`. Entities without a `foreignId` (or where `infuseData` returns `null`) have `infusion: {}`.