transformData

hooks

Source Code | Documentation

See also: transformers utils/mutateData

Transforms each item in context.data using the provided transformer function. The transformer receives each item and can mutate it in place or return a new object. Commonly used with built-in transformers like lowercase, trim, or setNow.

  import { transformData } from 'feathers-utils/hooks';

Example

import { transformData, lowercase } from 'feathers-utils/transformers'

app.service('users').hooks({
  before: { create: [transformData(lowercase('email'))] }
})

Type declaration

Show Type Declarations

/**
 * Transforms each item in `context.data` using the provided transformer function.
 * The transformer receives each item and can mutate it in place or return a new object.
 * Commonly used with built-in transformers like `lowercase`, `trim`, or `setNow`.
 *
 * @example
 * ```ts
 *
 *
 * app.service('users').hooks({
 *   before: { create: [transformData(lowercase('email'))] }
 * })
 * ```
 *
 * @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.

Transformer	Description
lowercase	Transforms the specified fields of an item to lowercase.
omit	Omit the specified fields from an item.
parseDate	Parses the specified fields of an item into Date objects.
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.