Field Hooks

Field Hooks are Hooks that run on Documents on a per-field basis. They allow you to execute your own logic during specific events of the Document lifecycle. Field Hooks offer incredible potential for isolating your logic from the rest of your Collection Hooks and Global Hooks.

To add Hooks to a Field, use the hooks property in your Field Config:

1import type { Field } from 'payload';
2
3export const FieldWithHooks: Field = {
4  // ...
5  hooks: { 
6    // ...
7  },
8}

Config Options

All Field Hooks accept an array of synchronous or asynchronous functions. These functions can optionally modify the return value of the field before the operation continues. All Field Hooks are formatted to accept the same arguments, although some arguments may be undefined based the specific hook type.

To add hooks to a Field, use the hooks property in your Field Config:

1import type { Field } from 'payload';
2
3const FieldWithHooks: Field = {
4  name: 'name',
5  type: 'text',
6  hooks: {
7    beforeValidate: [(args) => {...}],
8    beforeChange: [(args) => {...}],
9    beforeDuplicate: [(args) => {...}],
10    afterChange: [(args) => {...}],
11    afterRead: [(args) => {...}],
12  }
13}

The following arguments are provided to all Field Hooks:

Option	Description
`collection`	The Collection in which this Hook is running against. If the field belongs to a Global, this will be `null`.
`context`	Custom context passed between Hooks. More details.
`data`	In the `afterRead` hook this is the full Document. In the `create` and `update` operations, this is the incoming data passed through the operation.
`field`	The Field which the Hook is running against.
`findMany`	Boolean to denote if this hook is running against finding one, or finding many within the `afterRead` hook.
`global`	The Global in which this Hook is running against. If the field belongs to a Collection, this will be `null`.
`operation`	The name of the operation that this hook is running within. Useful within `beforeValidate`, `beforeChange`, and `afterChange` hooks to differentiate between `create` and `update` operations.
`originalDoc`	In the `update` operation, this is the Document before changes were applied. In the `afterChange` hook, this is the resulting Document.
`overrideAccess`	A boolean to denote if the current operation is overriding Access Control.
`path`	The path to the Field in the schema.
`previousDoc`	In the `afterChange` Hook, this is the Document before changes were applied.
`previousSiblingDoc`	The sibling data of the Document before changes being applied, only in `beforeChange` and `afterChange` hook.
`previousValue`	The previous value of the field, before changes, only in `beforeChange` and `afterChange` hooks.
`req`	The Web Request object. This is mocked for Local API operations.
`schemaPath`	The path of the Field in the schema.
`siblingData`	The data of sibling fields adjacent to the field that the Hook is running against.
`siblingDocWithLocales`	The sibling data of the Document with all Locales.
`value`	The value of the Field.

beforeValidate

Runs before the update operation. This hook allows you to pre-process or format field data before it undergoes validation.

1import type { Field } from 'payload'
2
3const usernameField: Field = {
name: 'username',
type: 'text',
hooks: {
  beforeValidate: [
    ({ value }) => {
      // Trim whitespace and convert to lowercase
      return value.trim().toLowerCase()
    },
  ],
},
14}

In this example, the beforeValidate hook is used to process the username field. The hook takes the incoming value of the field and transforms it by trimming whitespace and converting it to lowercase. This ensures that the username is stored in a consistent format in the database.

beforeChange

Immediately following validation, beforeChange hooks will run within create and update operations. At this stage, you can be confident that the field data that will be saved to the document is valid in accordance to your field validations.

1import type { Field } from 'payload'
2
3const emailField: Field = {
name: 'email',
type: 'email',
hooks: {
  beforeChange: [
    ({ value, operation }) => {
      if (operation === 'create') {
        // Perform additional validation or transformation for 'create' operation
      }
      return value
    },
  ],
},
16}

In the emailField, the beforeChange hook checks the operation type. If the operation is create, it performs additional validation or transformation on the email field value. This allows for operation-specific logic to be applied to the field.

afterChange

The afterChange hook is executed after a field's value has been changed and saved in the database. This hook is useful for post-processing or triggering side effects based on the new value of the field.

1import type { Field } from 'payload'
2
3const membershipStatusField: Field = {
name: 'membershipStatus',
type: 'select',
options: [
  { label: 'Standard', value: 'standard' },
  { label: 'Premium', value: 'premium' },
  { label: 'VIP', value: 'vip' },
],
hooks: {
  afterChange: [
    ({ value, previousValue, req }) => {
      if (value !== previousValue) {
        // Log or perform an action when the membership status changes
        console.log(
          `User ID ${req.user.id} changed their membership status from ${previousValue} to ${value}.`,
        )
        // Here, you can implement actions that could track conversions from one tier to another
      }
    },
  ],
},
24}

In this example, the afterChange hook is used with a membershipStatusField, which allows users to select their membership level (Standard, Premium, VIP). The hook monitors changes in the membership status. When a change occurs, it logs the update and can be used to trigger further actions, such as tracking conversion from one tier to another or notifying them about changes in their membership benefits.

afterRead

The afterRead hook is invoked after a field value is read from the database. This is ideal for formatting or transforming the field data for output.

1import type { Field } from 'payload'
2
3const dateField: Field = {
name: 'createdAt',
type: 'date',
hooks: {
  afterRead: [
    ({ value }) => {
      // Format date for display
      return new Date(value).toLocaleDateString()
    },
  ],
},
14}

Here, the afterRead hook for the dateField is used to format the date into a more readable format using toLocaleDateString(). This hook modifies the way the date is presented to the user, making it more user-friendly.

beforeDuplicate

The beforeDuplicate field hook is called on each locale (when using localization), when duplicating a document. It may be used when documents having the exact same properties may cause issue. This gives you a way to avoid duplicate names on unique, required fields or when external systems expect non-repeating values on documents.

This hook gets called before the beforeValidate and beforeChange hooks are called.

By Default, unique and required text fields Payload will append "- Copy" to the original document value. The default is not added if your field has its own, you must return non-unique values from your beforeDuplicate hook to avoid errors or enable the disableDuplicate option on the collection. Here is an example of a number field with a hook that increments the number to avoid unique constraint errors when duplicating a document:

1import type { Field } from 'payload'
2
3const numberField: Field = {
4  name: 'number',
5  type: 'number',
6  hooks: {
7    // increment existing value by 1
8    beforeDuplicate: [({ value }) => {
9      return (value ?? 0) + 1
10    }],
11  }
12}

TypeScript

Payload exports a type for field hooks which can be accessed and used as follows:

1import type { FieldHook } from 'payload'
2
3// Field hook type is a generic that takes three arguments:
4// 1: The document type
5// 2: The value type
6// 3: The sibling data type
7
8type ExampleFieldHook = FieldHook<ExampleDocumentType, string, SiblingDataType>
9
10const exampleFieldHook: ExampleFieldHook = (args) => {
11  const {
12    value, // Typed as `string` as shown above
13    data, // Typed as a Partial of your ExampleDocumentType
14    siblingData, // Typed as a Partial of SiblingDataType
15    originalDoc, // Typed as ExampleDocumentType
16    operation,
17    req,
18  } = args
19
20  // Do something here...
21
22  return value // should return a string as typed above, undefined, or null
23}

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