transformData

Type declaration

/**
 * Make changes to items in `context.data`. Very flexible.
 *
 * @see https://utils.feathersjs.com/hooks/transform-data.html
 */
export declare const transformData: <
  T = Record<string, any>,
  H extends HookContext = HookContext,
>(
  transformer: TransformerFn<T, H>,
) => (context: H, next?: NextFunction) => Promise<any>

Argument	Type	Description
transformer	TransformerFn<T, H>

type	methods	multi
before, around	create, update, patch, remove	yes

transformData is a very flexible hook that allows you to transform the data. It can be used to modify the data before it is sent to the database. This can be useful for applying transformations to the data fields, adding default values, or modifying the data structure.

Async Transformations

This hook supports asynchronous transformations. You can return a promise from the hook to perform asynchronous operations before the data is processed. But be aware that this can lead to performance issues if the transformations are slow or if there are many records to process. When you need to call another service or perform a database query, it's usually better to create your own hook that fetches the necessary data before transformData is called.

You can use transformData like this:

import { transformData } from "feathers-utils/hooks";
import { getDataIsArray } from "feathers-utils/utils";

const myHook = () => async (context) => {
  const { data } = getDataIsArray(context);

  const users = await context.app.service("users").find({
    query: {
      id: { $in: data.map((d) => d.userId) },
    },
    paginate: false,
  });

  await transformData((item) => {
    // or whatever transformation you need
    item.userEmail = users.find((u) => u.id === item.userId)?.email;
    return item;
  })(context);
};

Transformers

'feathers-utils' provides a set of transformers that can be used with this hook. These transformers can be used to trim strings, convert dates, or omit fields from the data.

lowercase

Transforms the specified fields of an item to lowercase.

omit

Omit the specified fields from an item.

parseDate

pick

Picks the specified fields from an item.

setNow

Sets the specified fields of an item to the current date and time.

trim

Trims the specified fields of an item.