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Error messages

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Description

Eufemia Forms comes with built-in error messages. But you can also customize and override these messages by using the errorMessages property both on fields (field level) and on the Form.Handler (global level).

You may use the errorMessages property for two purposes:

  • Provide your own error messages.
  • Overwrite the default error messages.

Both can be done on a global level or on a field level.

However, for when overwriting the default error messages on a global level, you can also use internationalization (i18n).

Error object

Use new Error with a message to display a custom error message.

render(<Field.PhoneNumber error={new Error('Show this message')} />)

Or in case of a validator:

const myValidator = (value) => {
  // Your validation logic
  return new Error('Show this message')
}


render(<Field.PhoneNumber onBlurValidator={myValidator} />)

Reuse existing error messages in a validator function

You can reuse existing error messages in a validator function. The types of error messages available depend on the field type.

For example, you can reuse the Field.errorRequired error message in a validator function:

const myValidator = (value) => {
  // Your validation logic
  return new FormError('Field.errorRequired')
}


// Other options to reuse error messages, without using "FormError".
const myValidatorAlt = (value, { errorMessages }) => {
  return new Error(errorMessages['Field.errorRequired'])


  // Deprecated
  return new Error(errorMessages.required)
}


render(<Field.String onBlurValidator={myValidator} />)

FormError object

You can use the JavaScript Error object to display a custom error message:

import { Field } from '@dnb/eufemia/extensions/forms'


render(<Field.PhoneNumber error={new Error('Custom message')} />)

When it comes to re-using existing translations, you can also use the FormError object to display error messages.

You can provide either an existing translation key, such as:

  • Field.errorRequired - Displayed when the field is required and the user has not provided a value.
  • Field.errorPattern - Displayed when the user has provided a value that does not match the pattern.
import { FormError, Field } from '@dnb/eufemia/extensions/forms'


// - Error property
render(<Field.PhoneNumber error={new FormError('Field.errorRequired')} />)


// - Validator function
render(
  <Field.PhoneNumber
    onBlurValidator={() => {
      return new FormError('Field.errorRequired')
    }}
  />,
)

Overwrite existing keys

Per field, you can overwrite existing keys:

render(
  <Field.PhoneNumber
    errorMessages={{
      'Field.errorRequired': 'Display me, instead of the default message',
    }}
  />,
)

Custom keys in a field

You can also provide your own keys:

<Field.PhoneNumber
  error={new FormError('MyCustom.message')}
  errorMessages={{
    'MyCustom.message': 'Your custom error message',
  }}
/>

Custom keys in Form.Handler

Here is how you can provide your own keys or overwrite existing ones in a global errorMessages object inside the Form.Handler:

render(
  <Form.Handler
    errorMessages={{
      'MyCustom.message': 'Your custom error message',
      'Field.errorRequired': 'Display me, instead of the default message',
    }}
  >
    ...
  </Form.Handler>,
)

Localization of error messages

You can also provide localized error messages:

render(
  <Form.Handler
    errorMessages={{
      'en-GB': {
        'Field.errorRequired':
          'Display me, instead of the default message',
      },
      'nb-NO': {
        'Field.errorRequired': 'Vis meg istedenfor for standardmeldingen',
      },
    }}
  >
    ...
  </Form.Handler>,
)

Use translations to localize error messages

You can customize error messages via translations for the entire form:

import { Form } from '@dnb/eufemia/extensions/forms'


render(
  <Form.Handler
    translations={{
      'nb-NO': {
        // - Overwrite existing keys
        Field: { errorRequired: 'Display this error message instead' },
        'Field.errorRequired': 'Display this error message instead',


        // - Custom keys
        MyCustom: { key: 'Your custom error message' },
        'MyCustom.message': 'Your custom error message',
      },
    }}
  >
    <Field.String pattern="^([a-z]+)$" value="123" validateInitially />
  </Form.Handler>,
)

Error message in a field schema

You can define an error message in a schema for one field:

Using Zod schemas

import { Form, Field, z } from '@dnb/eufemia/extensions/forms'


const schema = z
  .string()
  .regex(
    /^([a-z]+)$/,
    'You can provide a custom message in the schema itself',
  )


render(
  <Form.Handler>
    <Field.String schema={schema} value="123" validateInitially />
  </Form.Handler>,
)

Using JSON Schema (Ajv)

import {
  Form,
  Field,
  makeAjvInstance,
} from '@dnb/eufemia/extensions/forms'


const ajv = makeAjvInstance()
const schema = {
  type: 'string',
  pattern: '^([a-z]+)$',
  errorMessage: 'You can provide a custom message in the schema itself',
} as const


render(
  <Form.Handler ajvInstance={ajv}>
    <Field.String schema={schema} value="123" validateInitially />
  </Form.Handler>,
)

Error message in a global schema

You can also define an error message in a schema for the entire form:

Using Zod schemas

import { Form, Field, z } from '@dnb/eufemia/extensions/forms'


const schema = z.object({
  myKey: z
    .string()
    .regex(
      /^([a-z]+)$/,
      'You can provide a custom message in the schema itself',
    ),
})


render(
  <Form.Handler schema={schema}>
    <Field.String path="/myKey" value="123" validateInitially />
  </Form.Handler>,
)

Using JSON Schema (Ajv)

const ajv = makeAjvInstance()
const schema = {
  type: 'object',
  properties: {
    myKey: {
      type: 'string',
      pattern: '^([a-z]+)$',
      errorMessage:
        'You can provide a custom message in the schema itself',
    },
  },
} as const


render(
  <Form.Handler schema={schema} ajvInstance={ajv}>
    <Field.String path="/myKey" value="123" validateInitially />
  </Form.Handler>,
)

Or in a Form.Handler schema with several validation rules:

Using Zod schemas

import { Form, Field, z } from '@dnb/eufemia/extensions/forms'


const schema = z.object({
  myKey: z
    .string()
    .min(2, 'minLength message in provider schema')
    .max(3, 'maxLength message in provider schema'),
})


render(
  <Form.Handler schema={schema}>
    <Field.String path="/myKey" value="123" validateInitially />
  </Form.Handler>,
)

Using JSON Schema (Ajv)

import {
  Form,
  Field,
  makeAjvInstance,
} from '@dnb/eufemia/extensions/forms'


const ajv = makeAjvInstance()
const schema = {
  type: 'object',
  properties: {
    myKey: {
      type: 'string',
      minLength: 2,
      maxLength: 3,
      errorMessage: {
        minLength: 'minLength message in provider schema',
        maxLength: 'maxLength message in provider schema',
      },
    },
  },
} as const


render(
  <Form.Handler schema={schema} ajvInstance={ajv}>
    <Field.String path="/myKey" value="123" validateInitially />
  </Form.Handler>,
)

Levels of errorMessages

You can provide custom error message different levels with the errorMessages property:

  1. On the Form.Handler (Provider) level.
  2. On the Form.Handler (Provider) level with a JSON Pointer path.
  3. On the field level.

The levels are prioritized in the order above, so the field level error message will overwrite all other levels.

Here is an example of how to do expose a custom error message for the Field.errorRequired validation rule on all levels:

import {
  Form,
  Field,
  makeAjvInstance,
} from '@dnb/eufemia/extensions/forms'


const ajv = makeAjvInstance()


render(
  <Form.Handler
    ajvInstance={ajv}
    errorMessages={{
      // Level 1
      'Field.errorRequired': 'Or on the provider',
      '/myKey': {
        // Level 2
        'Field.errorRequired': 'Or on the provider for just one field',
      },
    }}
  >
    <Field.String
      path="/myKey"
      errorMessages={{
        // Level 3
        'Field.errorRequired': 'Or on a single Field itself',
      }}
    />
  </Form.Handler>,
)

Demos

Code Editor
<Form.Handler
  errorMessages={{
    // Level 1
    'Field.errorPattern': 'Or on the provider',
    '/myKey': {
      // Level 2
      'Field.errorPattern': 'Or on the provider for just one field',
    },
  }}
>
  <Field.String
    errorMessages={{
      // Level 3
      'Field.errorPattern': 'Or on a single Field itself',
    }}
    path="/myKey"
    value="abc"
    pattern="^[0-9]+$"
    validateInitially
  />
</Form.Handler>