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Version: v5

Validation

When the form is submitted, the form data is validated to conform to the given JSON schema;

As of version 5, as a result of decoupling the validation implementation from the Form, a validator implementation is required to be passed to all Forms. React Json Schema Form provides a default @rjsf/validator-ajv6 implementation that uses version 6 of the ajv validator.

NOTE: The ajv6 validator has been deprecated from the outset in favor of the @rjsf/validator-ajv8 and is provided primarily to assist in code migrations

It also provides a new @rjsf/validator-ajv8 implementation that uses version 8 of the ajv validator. The error messages generated by this new validator differ from those provided by the original validator due to it using a newer version. If you depend on having specifically formatted messages, then using this validator would constitute a breaking change for you.

It is also possible for you to provide your own implementation if you desire, as long as it fulfills the ValidatorType interface specified in @rjsf/utils.

API documentation​

The documentation for the APIs associated with the AJV 8 validator package can be found here

Precompiled validators​

In 5.7.0, support for precompiled validators was added to the @rjsf/validator-ajv8 package. The main use case for this is to overcome issues with unsafe-eval warnings from the browser caused by strict Content Security Policy settings. See the Standalone Validation Code section of the AJV documentation for more details about precompiled validators.

Due to how RJSF uses the AJV validator in determining anyOf/oneOf selections and how it resolves dependencies, if-then-else and references ($ref) in schemas via the retrieveSchema() utility method, RJSF provides its own schema compilation API built on-top-of the one provided by AJV 8. If you are wanting to use a precompiled validator, two steps are required:

  1. Precompiling the schema into a set of validator functions
  2. Providing those precompiled validator functions to a ValidatorType implementation in the Form

Schema precompilation​

The first step in the process is to compile a schema into a set of validator functions that are saved into a commonJS-based Javascript file. The @rjsf/validator-ajv8 package exports the compileSchemaValidators() function that does this. It is expected that this function will be used in a manner similar to the following:

const compileSchemaValidators = require('@rjsf/validator-ajv8/dist/compileSchemaValidators').default;
const yourSchema = require('path_to/yourSchema'); // If your schema is a js file

compileSchemaValidators(yourSchema, 'path_to/yourCompiledSchema.js');

If you are currently using the customizeValidator() function to provide additionalMetaSchemas, customFormats, ajvOptionsOverrides and/or ajvFormatOptions then you can pass those in as the optional third parameter to the compileSchemaValidators() function in a manner similar to:

const { compileSchemaValidators } = require('@rjsf/validator-ajv8');
const yourSchema = require('path_to/yourSchema.json'); // If your schema is a json file

const options = {
  additionalMetaSchemas: [require('ajv/lib/refs/json-schema-draft-06.json')],
  customFormats: { 'phone-us': /\(?\d{3}\)?[\s-]?\d{3}[\s-]?\d{4}$/, 'area-code': /\d{3}/ },
  ajvOptionsOverrides: {
    $data: true,
    verbose: true,
  },
  ajvFormatOptions: {
    mode: 'fast',
  },
};

compileSchemaValidators(yourSchema, 'path_to/yourCompiledSchema.js', options);

It is highly recommended to create a compileYourSchema.js file (or what ever name you want) with code similar to what is shown above and then, using node, run the code as follows:

node compileYourSchema.js

NOTE: You must have your schema provided within a file that can be parsed and turned into the set of precompiled validator functions.

Additional Note: If you are using Webpack or NextJS and are encountering an issue resolving fs during development, consult this blog post for how to solve the issue.

Using the precompiled validator​

After you have completed step 1 having generated your precompiled schema functions into the yourCompiledSchema.js output file (or whatever you called it), then you need to create a ValidatorType implementation from it to use in the Form. The @rjsf/validator-ajv8 package exports the createPrecompiledValidator() function for this. Here is an example of how to use your precompiled validator with your Form:

import { createPrecompiledValidator, ValidatorFunctions } from '@rjsf/validator-ajv8';
import Form from '@rjsf/core'; // Or whatever theme you use

import yourSchema from 'path_to/yourSchema'; // This needs to be the same file that was precompiled
import * as precompiledValidator from 'path_to/yourCompiledSchema';

const validator = createPrecompiledValidator(precompiledValidator as ValidatorFunctions);

render(<Form schema={schema} validator={validator} />, document.getElementById('app'));

Dynamically pre-compiling validators​

For more advanced cases when schema needs to be precompiled on request - compileSchemaValidatorsCode can be used.

import { compileSchemaValidatorsCode } from '@rjsf/validator-ajv8/dist/compileSchemaValidators';

const code = compileSchemaValidatorsCode(schema, options);

For the most part it is the same as compileSchemaValidators, but instead of writing the file - it returns generated code directly.

To use it on browser side - some modifications are needed to provide runtime dependencies in generated code needs to be provided.

Example implementation of it:

import type { ValidatorFunctions } from '@rjsf/validator-ajv8';

import ajvRuntimeEqual from 'ajv/dist/runtime/equal';
import {
  parseJson as ajvRuntimeparseJson,
  parseJsonNumber as ajvRuntimeparseJsonNumber,
  parseJsonString as ajvRuntimeparseJsonString,
} from 'ajv/dist/runtime/parseJson';
import ajvRuntimeQuote from 'ajv/dist/runtime/quote';
// import ajvRuntimeRe2 from 'ajv/dist/runtime/re2';
import ajvRuntimeTimestamp from 'ajv/dist/runtime/timestamp';
import ajvRuntimeUcs2length from 'ajv/dist/runtime/ucs2length';
import ajvRuntimeUri from 'ajv/dist/runtime/uri';
import * as ajvFormats from 'ajv-formats/dist/formats';

// dependencies to replace in generated code, to be provided by at runtime
const validatorsBundleReplacements: Record<string, [string, unknown]> = {
  // '<code to be replaced>': ['<variable name to use as replacement>', <runtime dependency>],
  'require("ajv/dist/runtime/equal").default': ['ajvRuntimeEqual', ajvRuntimeEqual],
  'require("ajv/dist/runtime/parseJson").parseJson': ['ajvRuntimeparseJson', ajvRuntimeparseJson],
  'require("ajv/dist/runtime/parseJson").parseJsonNumber': ['ajvRuntimeparseJsonNumber', ajvRuntimeparseJsonNumber],
  'require("ajv/dist/runtime/parseJson").parseJsonString': ['ajvRuntimeparseJsonString', ajvRuntimeparseJsonString],
  'require("ajv/dist/runtime/quote").default': ['ajvRuntimeQuote', ajvRuntimeQuote],
  // re2 by default is not in dependencies for ajv and so is likely not normally used
  // 'require("ajv/dist/runtime/re2").default': ['ajvRuntimeRe2', ajvRuntimeRe2],
  'require("ajv/dist/runtime/timestamp").default': ['ajvRuntimeTimestamp', ajvRuntimeTimestamp],
  'require("ajv/dist/runtime/ucs2length").default': ['ajvRuntimeUcs2length', ajvRuntimeUcs2length],
  'require("ajv/dist/runtime/uri").default': ['ajvRuntimeUri', ajvRuntimeUri],
  // formats
  'require("ajv-formats/dist/formats")': ['ajvFormats', ajvFormats],
};

const regexp = new RegExp(
  Object.keys(validatorsBundleReplacements)
    .map((key) => key.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&'))
    .join('|'),
  'g'
);

function wrapAjvBundle(code: string) {
  return `function(${Object.values(validatorsBundleReplacements)
    .map(([name]) => name)
    .join(', ')}){\nvar exports = {};\n${code.replace(
    regexp,
    (req) => validatorsBundleReplacements[req][0]
  )};\nreturn exports;\n}`;
}

const windowValidatorOnLoad = '__rjsf_validatorOnLoad';
const schemas = new Map<
  string,
  { promise: Promise<ValidatorFunctions>; resolve: (result: ValidatorFunctions) => void }
>();
if (typeof window !== 'undefined') {
  // @ts-ignore
  window[windowValidatorOnLoad] = (loadedId: string, fn: (...args: unknown[]) => ValidatorFunctions) => {
    const validator = fn(...Object.values(validatorsBundleReplacements).map(([, dep]) => dep));
    let validatorLoader = schemas.get(loadedId);
    if (validatorLoader) {
      validatorLoader.resolve(validator);
    } else {
      throw new Error(`Unknown validator loaded id="${loadedId}"`);
    }
  };
}

/**
 * Evaluate precompiled validator in browser using script tag
 * @param id Identifier to avoid evaluating the same code multiple times
 * @param code Code generated server side using `compileSchemaValidatorsCode`
 * @param nonce nonce attribute to be added to script tag (https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/nonce#using_nonce_to_allowlist_a_script_element)
 */
export function evaluateValidator(id: string, code: string, nonce: string): Promise<ValidatorFunctions> {
  let maybeValidator = schemas.get(id);
  if (maybeValidator) return maybeValidator.promise;
  let resolveValidator: (result: ValidatorFunctions) => void;
  const validatorPromise = new Promise<ValidatorFunctions>((resolve) => {
    resolveValidator = resolve;
  });
  schemas.set(id, {
    promise: validatorPromise,
    resolve: resolveValidator!,
  });

  const scriptElement = document.createElement('script');

  scriptElement.setAttribute('nonce', nonce);
  scriptElement.text = `window["${windowValidatorOnLoad}"]("${id}", ${wrapAjvBundle(code)})`;

  document.body.appendChild(scriptElement);
  return validatorPromise;
}

From React component this can be used as following:

let [precompiledValidator, setPrecompiledValidator] = React.useState<ValidatorFunctions>();
React.useEffect(() => {
  evaluateValidator(
    schemaId, // some schema id to avoid evaluating it multiple times
    code, // result of compileSchemaValidatorsCode returned from the server
    nonce // nonce script tag attribute to allow this ib content security policy for the page
  ).then(setPrecompiledValidator);
}, [entityType.id]);

if (!precompiledValidator) {
  // render loading screen
}
const validator = createPrecompiledValidator(precompiledValidator, schema);

Live validation​

By default, form data are only validated when the form is submitted or when a new formData prop is passed to the Form component.

You can enable live form data validation by passing a liveValidate prop to the Form component, and set it to true. Then, every time a value changes within the form data tree (e.g. the user entering a character in a field), a validation operation is performed, and the validation results are reflected into the form state.

Be warned that this is an expensive strategy, with possibly strong impact on performances.

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import validator from '@rjsf/validator-ajv8';

const schema: RJSFSchema = {
  type: ['string'],
  const: 'test',
};

const formData = 'a';

render(<Form schema={schema} formData={formData} validator={validator} liveValidate />, document.getElementById('app'));

Validate form programmatically​

It is possible to programmatically validate a form using the validateForm() function on Form. Add a ref to your Form component and call the validateForm() method to validate the form programmatically. The validateForm() method returns true if the form is valid, false otherwise. If you have provided an onError callback it will be called with the list of errors when the validatorForm() method returns false.

import { createRef } from 'react';
import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import validator from '@rjsf/validator-ajv8';

const formRef = createRef();
const onError = (errors) => alert(errors);

const schema: RJSFSchema = {
  type: 'string',
};

render(<Form schema={schema} validator={validator} onError={onError} ref={formRef} />, document.getElementById('app'));

if (formRef.current.validateForm()) {
  alert('Form is valid');
}

HTML5 Validation​

By default, the form uses HTML5 validation. This may cause unintuitive results because the HTML5 validation errors (such as when a field is required) may be displayed before the form is submitted, and thus these errors will display differently from the react-jsonschema-form validation errors. You can turn off HTML validation by setting the noHtml5Validate to true.

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import validator from '@rjsf/validator-ajv8';

const schema: RJSFSchema = {
  type: 'object',
  properties: {
    name: {
      type: 'string',
      required: true,
    },
  },
};

render(<Form schema={schema} validator={validator} noHtml5Validate />, document.getElementById('app'));

Custom validation rules​

Form data is always validated against the JSON schema.

But it is possible to define your own custom validation rules that will run in addition to (and after) the validator implementation. This is especially useful when the validation depends on several interdependent fields.

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import validator from '@rjsf/validator-ajv8';

function customValidate(formData, errors, uiSchema) {
  if (formData.pass1 !== formData.pass2) {
    errors.pass2.addError("Passwords don't match");
  }
  return errors;
}

const schema: RJSFSchema = {
  type: 'object',
  properties: {
    pass1: { type: 'string', minLength: 3 },
    pass2: { type: 'string', minLength: 3 },
  },
};

render(<Form schema={schema} validator={validator} customValidate={customValidate} />, document.getElementById('app'));

Notes:

  • The customValidate() function must implement the CustomValidator interface found in @rjsf/utils.
  • The customValidate() function must always return the errors object received as second argument.
  • The customValidate() function is called after the JSON schema validation.
  • The customValidate() function is passed the uiSchema as the third argument. This allows the customValidate() function to be able to derive additional information from it for generating errors.

Custom error messages​

Validation error messages are provided by the JSON Schema validation by default. If you need to change these messages or make any other modifications to the errors from the JSON Schema validation, you can define a transform function that receives the list of JSON Schema errors and returns a new list.

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import validator from '@rjsf/validator-ajv8';

function transformErrors(errors, uiSchema) {
  return errors.map((error) => {
    if (error.name === 'pattern') {
      error.message = 'Only digits are allowed';
    }
    return error;
  });
}

const schema: RJSFSchema = {
  type: 'object',
  properties: {
    onlyNumbersString: { type: 'string', pattern: '^\\d*$' },
  },
};

render(
  <Form schema={schema} validator={validator} transformErrors={transformErrors} />,
  document.getElementById('app')
);

Notes:

  • The transformErrors() function must implement the ErrorTransformer interface found in @rjsf/utils.
  • The transformErrors() function must return the list of errors. Modifying the list in place without returning it will result in an error.
  • The transformErrors() function is passed the uiSchema as the second argument. This allows the transformErrors() function to be able to derive additional information from it for transforming errors.

Each element in the errors list passed to transformErrors is a RJSFValidationError interface (in @rjsf/utils) and has the following properties:

  • name: optional name of the error, for example, "required" or "minLength"
  • message: optional message, for example, "is a required property" or "should NOT be shorter than 3 characters"
  • params: optional object with the error params returned by ajv (see doc for more info).
  • property: optional string in Javascript property accessor notation to the data path of the field with the error. For example, .name or .first-name.
  • schemaPath: optional JSON pointer to the schema of the keyword that failed validation. For example, #/fields/firstName/required. (Note: this may sometimes be wrong due to a bug in ajv).
  • stack: full error name, for example ".name is a required property".

Error List Display​

To take control over how the form errors are displayed, you can define an error list template for your form. This list is the form global error list that appears at the top of your forms.

An error list template is basically a React stateless component being passed errors as props, so you can render them as you like:

import { Form } from '@rjsf/core';
import { RJSFSchema, ErrorListProps } from "@rjsf/utils";
import validator from "@rjsf/validator-ajv8";

function ErrorListTemplate(props: ErrorListProps) {
  const { errors } = props;
  return (
    <div>
      <h2>Custom error list</h2>
      <ul>
        {errors.map(error => (
            <li key={error.stack}>
              {error.stack}
            </li>
          ))}
      </ul>
    </div>
  );
}

const schema: RJSFSchema = {
  type: "string",
  const: "test"
};

render((
  <Form schema={schema}
        validator={validator}
        showErrorList='top'
        formData={""}
        liveValidate
        templates: {{ ErrorListTemplate }} />
), document.getElementById("app"));

Note: Your custom ErrorList template will only render when showErrorList is top or botttom.

The following props are passed to ErrorList as defined by the ErrorListProps interface in @rjsf/utils:

  • errors: An array of the errors.
  • errorSchema: The errorSchema constructed by Form.
  • schema: The schema that was passed to Form.
  • uiSchema: The uiSchema that was passed to Form.
  • formContext: The formContext object that you passed to Form.

The case of empty strings​

When a text input is empty, the field in form data is set to undefined. However, since undefined isn't a valid JSON value according to the official JSON standard (ECMA-404, Section 5), the values get stored as null.

String fields that use enum and a select widget will have an empty option at the top of the options list that when selected will result in the field being null.

One consequence of this is that if you have an empty string in your enum array, selecting that option in the select input will cause the field to be set to null, not an empty string.

If you want to have the field set to a default value when empty you can provide a ui:emptyValue field in the uiSchema object.

Custom meta schema validation​

To have your schemas validated against any other meta schema than draft-07 (the current version of JSON Schema), make sure your schema has a $schema attribute that enables the validator to use the correct meta schema. For example:

{
  "$schema": "http://json-schema.org/draft-04/schema#",
  ...
}

Note that react-jsonschema-form supports JSON Schema draft-07 by default. To support additional meta schemas, you can create and pass to the Form component a customized @rjsf/validator-ajv8:

additionalMetaSchemas​

The additionalMetaSchemas prop allows you to validate the form data against one (or more than one) JSON Schema meta schema, for example, JSON Schema draft-04. You can import a meta schema as follows:

const metaSchemaDraft04 = require('ajv/lib/refs/json-schema-draft-04.json');

In this example schema passed as props to Form component can be validated against draft-07 (default) and by draft-04 (added), depending on the value of $schema attribute.

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import { customizeValidator } from '@rjsf/validator-ajv6';

const validator = customizeValidator({
  additionalMetaSchemas: [metaSchemaDraft04],
});

const schema: RJSFSchema = {
  $schema: 'http://json-schema.org/draft-04/schema#',
  type: 'string',
};

return <Form schema={schema} validator={validator} />;

NOTE: This syntax works only for the @rjsf/validator-ajv6 validator; if you only use the draft-04 schema, and you want to use the @rjsf/validator-ajv8 you can do the following:

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import { customizeValidator } from '@rjsf/validator-ajv8';
import AjvDraft04 from 'ajv-draft-04';

const validator = customizeValidator({ AjvClass: AjvDraft04 });

const schema: RJSFSchema = {
  $schema: 'http://json-schema.org/draft-04/schema#',
  type: 'string',
};

return <Form schema={schema} validator={validator} />;

customFormats​

Pre-defined semantic formats are limited. react-jsonschema-form adds two formats, color and data-url, to support certain alternative widgets. To add formats of your own, you can create and pass to the Form component a customized @rjsf/validator-ajv8:

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import { customizeValidator } from '@rjsf/validator-ajv8';

const schema: RJSFSchema = {
  type: 'string',
  format: 'phone-us',
};

const customFormats = {
  'phone-us': /\(?\d{3}\)?[\s-]?\d{3}[\s-]?\d{4}$/,
};

const validator = customizeValidator({ customFormats });

render(<Form schema={schema} validator={validator} />, document.getElementById('app'));

Format values can be anything AJV's addFormat method accepts.

Async validation​

Handling async errors is an important part of many applications. Support for this is added in the form of the extraErrors prop.

For example, a request could be made to some backend when the user submits the form. If that request fails, the errors returned by the backend should be formatted like in the following example.

import { Form } from '@rjsf/core';
import { RJSFSchema, ErrorSchema } from '@rjsf/utils';
import validator from '@rjsf/validator-ajv8';

const schema: RJSFSchema = {
  type: 'object',
  properties: {
    foo: {
      type: 'string',
    },
    candy: {
      type: 'object',
      properties: {
        bar: {
          type: 'string',
        },
      },
    },
  },
};

const extraErrors: ErrorSchema = {
  foo: {
    __errors: ['some error that got added as a prop'],
  },
  candy: {
    bar: {
      __errors: ['some error that got added as a prop'],
    },
  },
};

render(<Form schema={schema} validator={validator} extraErrors={extraErrors} />, document.getElementById('app'));

An important note is that these errors are "display only" and will not block the user from submitting the form again.

ajvOptionsOverrides​

In version 5, with the advent of the decoupling of the validation implementation from the Form, it is now possible to provide additional options to the ajv instance used within @rjsf/validator-ajv8. For instance, if you need more information from ajv about errors via the verbose option, now you can turn it on!

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import { customizeValidator } from '@rjsf/validator-ajv8';

const schema: RJSFSchema = {
  type: 'string',
  format: 'phone-us',
};

const ajvOptionsOverrides = {
  verbose: true,
};

const validator = customizeValidator({ ajvOptionsOverrides });

render(<Form schema={schema} validator={validator} />, document.getElementById('app'));

Using the raw Ajv instance​

The customizeValidator() function returns the AJV8Validator (or AJV6Validator depending on the library you use) implementation class, which has an internal raw ajv instance within it. If you need to do some deep customization of the instance using any of the ajv libraries (like ajv-keywords), you can do so using this raw instance as follows:

import { customizeValidator } from '@rjsf/validator-ajv6';
import ajvKeywords from 'ajv-keywords';

const validator = customizeValidator();
ajvKeywords(validator.ajv, ['your-keyword']);

// use your update validator with a `Form`

Ajv8 validator differences​

There are a few differences in configuring the Ajv 8 validator. First, there are many things to be aware of related to internal migration from Ajv 6 to 8; see the migration guide for more information.

One big difference is that Ajv 8 dropped support for any JSON Schema version before draft-06. So if your schema is using an older format, you have to either upgrade it or stick with the @rjsf/validator-ajv6.

Our implementation of @rjsf/validator-ajv8 also utilizes Ajv's internal cache to avoid unnecessarily re-compiling schemas, which can be an expensive operation. The cache key is the schema $id.

The ajvOptionsOverrides for the Ajv 8 validator are the ones supported by that version and not the Ajv 6 validator. Second, the data formats previously provided in Ajv 6 now need to be added explicitly using the ajv-formats package. A new ajvFormatOptions option is available on the customizeValidator() API to be able to configure this. Additionally, a new AjvClass option is available on the customizeValidator() API to support using one of the other JSON schema versions provided by Ajv 8 besides the draft-07 default. Finally, the Ajv 8 validator supports the localization of error messages.

ajvFormatOptions​

By default, ALL formats are being added to the default @rjsf/validator-ajv8 that you get when you import it.

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import validator from '@rjsf/validator-ajv8';

const schema: RJSFSchema = {
  type: 'string',
  format: 'email',
};

render(<Form schema={schema} validator={validator} />, document.getElementById('app'));

If you don't actually need any of the ajv-formats and want to reduce the memory footprint, then you can turn it off as follows:

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import { customizeValidator } from '@rjsf/validator-ajv8';

const schema: RJSFSchema = {
  type: 'string',
};

const validator = customizeValidator({ ajvFormatOptions: false });

render(<Form schema={schema} validator={validator} />, document.getElementById('app'));

If you only need some of them, you can pass any of the options to the formatter:

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import { customizeValidator } from '@rjsf/validator-ajv8';

const schema: RJSFSchema = {
  type: 'string',
  format: 'date',
};

const validator = customizeValidator({ ajvFormatOptions: ['date'] });
// or
// const validator = customizeValidator({ ajvFormatOptions: { mode: "fast", formats: ["date"], keywords: true } });

render(<Form schema={schema} validator={validator} />, document.getElementById('app'));

AjvClass​

By default, the @rjsf/validator-ajv8 uses the draft-07 schema version. It is possible to use one of the other version it supports, like draft-2019-09 or draft-2020-12. NOTE: draft-2020-12 has breaking changes and hasn't been fully tested with @rjsf.

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import { customizeValidator } from '@rjsf/validator-ajv8';
import Ajv2019 from 'ajv/dist/2019';

const schema: RJSFSchema = {
  type: 'string',
  format: 'date',
};

const validator = customizeValidator({ AjvClass: Ajv2019 });
// or
// const validator = customizeValidator({ AjvClass: Ajv2020 });

render(<Form schema={schema} validator={validator} />, document.getElementById('app'));

Localization (L12n) support​

The Ajv 8 validator supports the localization of error messages using ajv-i18n. In addition, you may provide a custom solution by implementing a function that conforms to the Localizer interface if your language is not supported.

import { ErrorObject } from 'ajv';
/** The type describing a function that takes a list of Ajv `ErrorObject`s and localizes them
 */
export type Localizer = (errors?: null | ErrorObject[]) => void;

NOTE: The ajv-i18n validators implement the Localizer interface.

Some examples​

Using a specific locale while including all of ajv-i18n:

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import { customizeValidator } from '@rjsf/validator-ajv8';
import localizer from 'ajv-i18n';

const schema: RJSFSchema = {
  type: 'string',
};

const validator = customizeValidator({}, localizer.it);

render(<Form schema={schema} validator={validator} />, document.getElementById('app'));

Using a specific locale minimizing the bundle size

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import { customizeValidator } from '@rjsf/validator-ajv8';
import spanishLocalizer from 'ajv-i18n/localize/es';

const schema: RJSFSchema = {
  type: 'string',
};

const validator = customizeValidator({}, spanishLocalizer);

render(<Form schema={schema} validator={validator} />, document.getElementById('app'));

An example of a custom Localizer implementation:

import { Form } from '@rjsf/core';
import { RJSFSchema } from '@rjsf/utils';
import { customizeValidator } from '@rjsf/validator-ajv8';
import { ErrorObject } from 'ajv';

function localize_ru(errors: null | ErrorObject[] = []) {
  if (!(errors && errors.length)) return;
  errors.forEach(function (error) {
    let outMessage = '';

    switch (error.keyword) {
      case 'pattern': {
        outMessage = 'должно соответствовать образцу "' + error.params.pattern + '"';
        break;
      }
      case 'required': {
        outMessage = 'поле обязательно для заполнения';
        break;
      }
      default:
        outMessage = error.message;
    }

    error.message = outMessage;
  });
}

const schema: RJSFSchema = {
  type: 'string',
};

const validator = customizeValidator({}, localize_ru);

render(<Form schema={schema} validator={validator} />, document.getElementById('app'));

NOTES:

  • If you provided your own function, modify the list in place.
  • You must process all the cases which you need by yourself. See the full list of possible cases here.
  • Each element in the errors list passed to the custom function represent a raw error object returned by ajv (see doc).