Validation - react-jsonschema-form documentation

Form data validation¶

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, everytime a value changes within the form data tree (eg. 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.

To disable validation entirely, you can set Form's noValidate prop to true.

HTML5 Validation¶

By default, required field errors will cause the browser to display its standard HTML5 required attribute error messages and prevent form submission. If you would like to turn this off, you can set Form's noHtml5Validate prop to true, which will set noValidate on the form element.

Custom validation¶

Form data is always validated against the JSON schema.

But it is possible to define your own custom validation rules. This is especially useful when the validation depends on several interdependent fields.

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

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

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

Notes: - The validate() function must always return the errors object received as second argument. - The validate() function is called after the JSON schema validation.

Custom string formats¶

Pre-defined semantic formats are limited. react-jsonschema-form adds two formats, color and data-url, to support certain alternative widgets. You can add formats of your own through the customFormats prop to your Form component:

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

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

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

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

Custom 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 only supports the latest version of JSON Schema, draft-07, by default. To support additional meta schemas pass them through the additionalMetaSchemas prop to your Form component:

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

render((
  <Form schema={schema} 
        additionalMetaSchemas={[additionalMetaSchemas]}/>
), document.getElementById("app"));

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.

additionalMetaSchemas also accepts more than one meta schema:

render((
  <Form schema={schema} 
        additionalMetaSchemas={[metaSchema1, metaSchema2]} />
), document.getElementById("app"));

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.

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

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

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

Notes: - The transformErrors() function must return the list of errors. Modifying the list in place without returning it will result in an error.

Each element in the errors list passed to transformErrors has the following properties:

name: name of the error, for example, "required" or "minLength"
message: message, for example, "is a required property" or "should NOT be shorter than 3 characters"
params: an object with the error params returned by ajv (see doc for more info).
property: a string in Javascript property accessor notation to the data path of the field with the error. For example, .name or ['first-name'].
stack: full error name, for example ".name is a required property".
schemaPath: 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 https://github.com/epoberezkin/ajv/issues/512).

Error List Display¶

To disable rendering of the error list at the top of the form, you can set the showErrorList prop to false. Doing so will still validate the form, but only the inline display will show.

render((
  <Form schema={schema}
        showErrorList={false} />
), document.getElementById("app"));

Note: you can also use your own ErrorList

The case of empty strings¶

When a text input is empty, the field in form data is set to undefined. 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 undefined.

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 undefined, 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.