1.0.0-beta.8 • Public • Published


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    An opinionated form validation tool for React apps.


    • Great UX out of the box
      Offers predefined set of strategies to provide superior user experience, incl. debounced async validations.

    • Framework agnostic
      It works with all state management tools (or without any). Only React is required.

    • Thin
      Layer doesn't own the form data. Don't need to change anything in the way you manage the state to start using it. Its main and only concern is form validation with superior UX.

    • Declarative
      All you have to do is to declare behavior via props and shape the look in the markup. Layer will take care of the rest.

    Table of Contents


    Website is WIP and not ready for mobiles yet, sorry.

    • Simple [ live · source ]
      Sync validations only.
    • Advanced [ live · source ]
      Sync & async validations, linked fields etc.


    Get it:

    # yarn 
    yarn add react-validation-layer
    # npm 
    npm install --save react-validation-layer


    As simple as:

    import ValidationLayer from 'react-validation-layer';
      data={{ email, password }}
        email: emailFieldConfig,
        password: passwordFieldConfig,
        onChange: onChangeHandler,
        onSubmit: onSubmitHandler,
      {layer => (
        <form onSubmit={layer.handleSubmit}>
          <input type="text" {...layer.getPropsFor('email')} />
          <span className={layer.getStatusFor('email')}>
          <input type="text" {...layer.getPropsFor('password')} />
          <span className={layer.getStatusFor('password')}>
          <button {...layer.getSubmitButtonProps()}>


    Layer requires 3 things to handle validation of the form:

    • data to validate and render
    • fields list with configurations
    • and onChange + onSubmit handlers.

    Some options can be set either on the global level (i.e. for all fields), or on the field level. field-level option has priority and overrides the global one.

    Required: no
    Default: 'form'

    type LayerId = string;

    The ID of the layer to avoid DOM ids collisions. This value is a namespace for generated DOM ids to ensure their uniqueness. Use it if you have few forms on a single page.

    Required: yes

    type Data = { [attr: string]: any };

    Object with the form data. Layer doesn't care about how you manage the state. You can use vanilla React, or Redux, or whatever as a state container. Just pack the data for the form into single object and pass it to validation layer. Object can be flat or nested (see next section). immutable structures are supported (no need to call toJS()).


    Required: yes

    type Field = boolean | {
      strategy?: Strategy,
      asyncStrategy?: AsyncStrategy,
      validate?: (value: Value, data: Data) => ValidationResults,
      validateAsync?: (value: Value, data: Data) => Promise<ValidationResults>,
      debounceInterval?: number,
      linkedFields?: Array<string | KeyPath>,
      filter?: (value: DomValue, data: Data) => boolean,
      transformBeforeStore?: (value: DomValue, data: Data) => Value,
      transformBeforeRender?: (value: Value, data: Data) => DomValue,
      handlers?: Handlers,
    type Fields = { [attribute: string]: Field | Fields };

    Object with form fields config. If a field doesn't have validations and other special handlers, then it must be set to true to let the layer know that this field exists, thus it can serve props for it.

    Flat structures
    In case if data is flat, fields object must also be flat:

    const data = {
      username: 'alex',
      email: '',
    const fields = {
      username: true, // nothing special about this field, but letting layer know about it
      email: { validate: email => !!email }, // config for `email` field

    Nested structures
    Sometimes data is nested, fields object must replicate the shape of the data object:

    const data = {
      username: 'alex',
      email: '',
      creditCard: {
        number: '1234567890',
        owner: 'ALEX FEDOSEEV',
    const fields = {
      username: true, // nothing special about this field, but letting layer know about it
      email: { validate: email => !!email }, // config for `email` field
      creditCard: { // replicating the shape
        number: { validate: number => !!number },
        owner: { validate: owner => !!owner },


    Can be set on global or on the field level. See props.strategy for details.


    Can be set on global or on the field level. See props.asyncStrategy for details.


    Required: no

    type Validate = (value: Value, data: Data) => ValidationResults;
    type ValidationResults = boolean | {
      valid: boolean,
      message?: string,
      status?: string,

    Validation function, which takes value and data object (the one that is passed to <ValidationLayer />). It can return either boolean or Object.

    ValidationResults as an object contains:

    • valid: boolean flag, tells if passed value is valid or not. Required.
    • message: usually a text string (or i18n id of a text string) which will show up in the view, when this result will be emitted. Actually it can be whatever you want, e.g. array of strings. Not required, if you don't use it.
    • status: suppose to identify css class, e.g. success or failure (those are defaults). Keep in mind that you can pass here any string to provide rich feedback to the user. E.g. when you validate credit card field, on successful validation instead of simple success status, you can pass visa / mastercard etc to display icon of the payment system. Not required, if you don't use it or fine with defaults. Also see props.statuses.

    NOTE: In case if you want to re-use validators somewhere else, react-validation-layer exposes normalizeValidationResults util, which takes result from the field.validate and normalizes it to ValidationResults object shape.

    import { normalizeValidationResults } from 'react-validation-layer';
    const normalizedValidationResults = normalizeValidationResults(field.validate(email));
    // => always object, e.g. `{ valid: true }`


    Required: no

    type ValidateAsync = (value: Value, data: Data) => Promise<ValidationResults>;

    Async validation function, which takes value and data object as well, but returns a Promise, which must be resolved with the same ValidationResults (see field.validate).


    Can be set on global or on the field level. See props.debounceInterval for details.


    Required: no

    type LinkedFields = Array<string | KeyPath>;

    Some fields might be dependent on each other and when the value of the one field is changed, another field might become valid or invalid, e.g. password & passwordConfirmation. Here you can define such relations.

    How it works: when you define linkedFields for the field, you instruct the layer: "When the value of this field is changed, also re-validate following fields". Validators of the linked fields will receive data object with updated value of the parent field.


    Required: no

    type Filter = (value: DomValue, data: Data) => boolean;

    Sometimes you want to filter out some user input. Filter function takes value and data object. If it returns false, then handler.onChange won't be triggered. It means that user's input will be ignored.

    NOTE: filter doesn't filter empty strings.


    Required: no

    type TransformBeforeStore = (value: DomValue, data: Data) => Value; is always a string. However, some attributes should be number by its nature or differentiate from the DOM representation in another way. To keep your data clean, you can provide transformation function, which will take string value from the DOM and transform it before send it to the data store. Here are few examples:

    • price field must be a number thus it can be safely used for calculations
    • in the view we want creditCard to be shown w/ spaces (eg 1234 5678 8765 4321), but inside the data store it should be spaceless: 1234567887654321.


    Required: no

    type TransformBeforeRender = (value: Value, data: Data) => DomValue;

    In a certain way, this is opposite to previous method. If you want to format your number or represent credit card w/ spaces in the form field, you can make it happen using this hook.


    Required: no

    Can be set on global or on the field level. This object is equal to props.handlers, except you can't define onSubmit handler here.


    Required: no
    Default: 'onFirstSuccessOrFirstBlur'

    type Strategy =
      | 'onFirstBlur'
      | 'onFirstChange'
      | 'onFirstSuccess'
      | 'onFirstSuccessOrFirstBlur'
      | 'onFirstSubmit'

    In most cases validation feedback should be provided as soon as possible, but not too soon. The question comes down to when to start to provide the feedback. It really depends on context. Strategies below won't provide any feedback until the specific moment, e.g. the first blur from the field or the first successful validation. All you have to do is to pick the most suitable one for your context. To understand the behavior of each strategy, add the following prefix to its name: "Start providing instant feedback on..."


    Validation Layer emits results for the single field as user types. Note that first feedback will be provided only after first change in this field.


    Validation Layer emits results on first blur. After first results were emitted—feedback is provided on every change in this field.


    Validation Layer emits results on first successful validation. After first results were emitted—feedback is provided on every change in this field.


    Validation Layer emits first results immediately on successful validation or on the first blur. After first results were emitted—feedback is provided on every change in this field.


    Validation Layer emits first results only after first submission attempt. After this results for each field are emitted on every change in this field until validation layer will be reseted or remounted.

    NOTE: After first submission of the form all fields are switched to onFirstSubmit strategy. It means that each field will receive feedback on every change in the field.


    Required: no
    Default: 'onChange'

    type AsyncStrategy =
      | 'onBlur'
      | 'onChange'

    Some validations can't be performed locally, e.g. on signup you want to validate if email from the input is available or already taken.


    There are 2 common ways to provide async feedback: request the server on every change or only on blur event. The first one is better in terms of UX, but creates significant load, so your client might become slow or server might feel bad. The blur option doesn't have this problem (at least not that much), but UX is definitely not the best, b/c user have to blur away from the field to get the feedback.

    What can we do about it to have the best of both worlds? The answer is to debounce on change async validations. What does it mean and how does it work: when user types something in in the form field, no external requests are triggered. Instead, it's put on hold. While user types, we wait. Once he stopped and there was no activity in the certain period—request is triggered.

    Validation layer does this out of the box. Just enable onChange async strategy and you're all set 🤘

    Also, it's a good UX to provide feedback in UI, when async validation is started. E.g. show a little spinner where you show your messages. Layer will let you know when to render it via layer.getAsyncStatusFor.


    This strategy triggers async validation only on blur event. Use this if even debounced validations hurt your server (but don't forget that you can setup debounceInterval, it might help to reduce the load).

    Few more things to keep in mind about async validations:

    • If sync strategy doesn't emit results -> layer doesn't trigger async validation.
    • If sync validation fails -> layer doesn't trigger async validation.
    • If sync validation succeeded and there is async validator for the field -> results will be emitted only from async validation: when async validation is triggered, layer will notify about the start of async validation, and when results will be resolved -> layer will serve them via props (as usual).
    • Layer does not perform any async validations on form submission as those validations will be performed on the server anyway within a single request (form submission). If server will reject submission and report errors, you can notify layer about it via callback, which accepts errors as argument (see props.handlers).

    N.B. Single strategy can be set for all the fields globally (root props strategy & asyncStrategy of <ValidationLayer />), as well as on per-field basis (field.strategy & field.asyncStrategy). Field-level strategy has higher priority, so, if it's set, it will override global strategy for current field.


    Required: no
    Default: 700

    type DebounceInterval = number;

    Configure amount of time (in ms) that layer should wait after last user activity before debounced async validation will be invoked.


    Required: no
    Default: { success: 'success', failure: 'failure' }

    type Statuses = {
      success: string,
      failure: string,

    These are default statuses for successful and failed validation results. Used, if no special values are provided from validators. Redefine it if you don't like the default ones.


    Required: yes

    type Handlers = {
      onChange?: (updatedData: UpdatedData) => void,
      onBlur?: (updatedData: UpdatedData) => void,
      onSubmit: (callbacks: OnSubmitCallbacks) => void,

    Tell the layer how to handle data updates and form submission. onChange and onBlur can be defined on the field level, so if every field has its own onChange method, on the props level it's not required. onBlur is always optional, but check out its section below for gotchas. onSubmit can be set only here and it is required.


    This is the method, which you must use to update form state in your app. It receive one argument from validation layer:

    type OnChange = (updatedData: UpdatedData) => void;
    type UpdatedData = {
      // Attribute that was updated
      attr: string,
      // If attribute is nested, this is key path to it
      keyPath: Array<string>,
      // Next value of attribute
      value: Value,
      // Value of `checked` DOM attribute
      checked: boolean,
      // Original data object (note: doesn't contain updated value)
      data: Data,
      // Original DOM event
      event: SyntheticInputEvent,

    If transformBeforeStore method is defined for this field, then the updatedData.value will be the returned value from this method, otherwise it's just a string from the DOM.

    NB onChange handler must put in state exactly the same value, that was passed to it from the layer, as layer uses it for validation.


    Usually you don't need this. So if it's the case, just ignore this handler. But if you actually want to do some stuff on blur event—don't override layer's handler in representation by putting onBlur prop on DOM input field directly, but provide it to the layer here and it will trigger it for you (with the same UpdatedData object as argument). Otherwise layer won't be able to handle blur events correctly. If you still want to redefine it from the representation, then see layer.notifyOnBlur.


    This method will be triggered on form submission if all fields of the form are passed validation. It receives object with 2 callbacks as argument:

    type OnSubmit = (callbacks: OnSubmitCallbacks) => void;
    type OnSubmitCallbacks = {
      onSuccess: () => void,
      onFailure: (errors: {}) => void,

    Invoke onSuccess after successful response from the server. It will reset internal validation layer state to its initial state.

    In case if something went wrong and your API responded with errors, invoke onFailure callback with these errors. Layer will pass them to representation in general way. Error object must replicate the shape of the data / fields objects, e.g.:

    const externalErrors = {
      email: 'Bad email',
      creditCard: {
        number: 'Bad credit card number',


    Validation layer requires children to be a function. This function receives single argument layer: an interface to the data from validation layer. Here is how it looks like:

    <ValidationLayer {...}>
      {layer => (
        <form onSubmit={layer.handleSubmit}>
          <input type="text" {...layer.getPropsFor('email')} />
          <input type="text" {...layer.getPropsFor('password')} />
          <button {...layer.getSubmitButtonProps()}>

    And here is what you can get:

    Providing paths to field data
    Usually you getSomething for specific field. In case if your fields object is flat, just pass attribute name to getter:

    const fields = { email: true };
    layer.getStatusFor('email') // <- string

    If you deal with nested structures and want to getSomething for the field, that's nested more than 1 level deep, provide key path to it:

    const fields = { user: { email: true } };
    layer.getStatusFor(['user', 'email']) // <- array of strings


    type GetPropsFor = (attr: string | KeyPath) => FieldDomProps;
    <input type="text" {...layer.getPropsFor('email')} />

    Returns props for general input DOM element (e.g. text input). It contains props like value, onChange etc. Apply it via spread operator.


    type GetCheckboxPropsFor = (attr: string | KeyPath) => FieldDomPropsWithChecked;
    <input type="checkbox" {...layer.getCheckboxPropsFor('subscribe')} />

    Returns props for checkbox. Same as getPropsFor, but with checked attribute.


    type GetRadioButtonPropsFor = (attr: string | KeyPath, value: string) => FieldDomPropsWithChecked;
    <input type="radio" {...layer.getRadioButtonPropsFor('paymentMethod', 'card')} />
    <input type="radio" {...layer.getRadioButtonPropsFor('paymentMethod', 'paypal')} />
    <input type="radio" {...layer.getRadioButtonPropsFor('paymentMethod', 'cash')} />

    When you render radio buttons, you must render one radio button for each possible value of the attribute. So, in addition to attribute, pass value as a second argument to get props for radio button.


    type GetCustomPropsFor = (attr: string | KeyPath, options: Options) => FieldDomProps | FieldDomPropsWithChecked;
    type Options = {
      value?: string,
      disabled?: ?boolean,
      getChecked?: (value: string) => boolean,

    Sometimes you want to do fancy stuff in UI and involve uncommon logic. If you can't achieve what you want with standard getters, here is constructor for you. It takes attribute name/key path + object with options (all keys are optional):

    • value: if provided, used to build radio button DOM id (NOT as value DOM attribute!). Should be a string. Use it only if you render radio button.
    • disabled: if provided, will be used for disabled DOM attribute. Should be boolean.
    • getChecked: if provided, will be used to get checked DOM attribute. It must be a function, which takes 1 argument: DOM value of the field, and returns boolean.


    type GetSubmitButtonProps = () => SubmitButtonDomProps;
    <button {...layer.getSubmitButtonProps()} />

    Returns props for submit button. Its only purpose is to disable button on form submission to prevent multiple submissions.


    type GetValidityFor = (attr: string | KeyPath) => boolean | null;

    Returns validity for the field. Keep in mind that in case if layer, according to strategy, isn't ready to provide feedback yet, it will return null.


    type GetStatusFor = (attr: string | KeyPath) => string;

    Returns status for a field. The one that is passed (or not) via validation results.

    Keep in mind that in case if layer, according to strategy, isn't ready to provide a feedback yet, it will return null.

    Also, in case if filed doesn't have a value, but still valid, status still is set to null. This is because the main use-case for status is CSS class name, but we don't want to paint everything green if field is empty.


    type IsSuccessFor = (attr: string | KeyPath) => boolean;

    Basically, it's a shorthand to get boolean result if success status is emitted for a field (instead of using comparison operators with layer.getStatusFor). Keep in mind, that emitting behavior is consistent with the layer.getStatusFor method: it will return false if, according to strategy, layer isn't ready to emit status or value is not present (even if it's a valid case for a field). To get the validity, use layer.getValidityFor


    type IsFailureFor = (attr: string | KeyPath) => boolean;

    Same as layer.isSuccessFor, but for the failure status.


    type GetMessageFor = (attr: string | KeyPath) => string;

    Returns message for the field. The one that is passed (or not) via validation results. Keep in mind that in case if layer, according to strategy, isn't ready to provide feedback yet, it will return null.


    type GetAsyncStatusFor = (attr: string | KeyPath) => string;

    Returns true if async validation is in process for the field.


    type GetSubmissionStatus = () => boolean;

    Returns true if form is submitting.


    type GetDomIdFor = (attr: string | KeyPath, value?: string) => string;
    <label htmlFor={layer.getDomIdFor('email')}>
    <input type="text" {...layer.getPropsFor('email')} />

    Returns id attribute of the DOM element for the field. You might need it for a various reasons, the most commonly used one is to provide DOM field id to <label /> for the field. Don't forget to provide value as second argument if you need id for radio button.


    type GetFieldIdFor = (attr: string | KeyPath) => string;

    Returns internal id of the field. You might need it for custom notifiers (see below).


    type NotifyOnChange = (fieldId: FieldId, value: Value) => void;

    If you do some fancy stuff with the field (e.g. update its value via JS / third-party tool, e.g. date picker), then use this method to notify layer about the change, so it can perform validations.


    type NotifyOnBlur = (
      fieldId: FieldId,
      value: Value,
      event: SyntheticInputEvent,
    ) => void;

    Same as layer.notifyOnChange, but to notify layer about blur events. You might need it in case if you've redefined onBlur handler of the DOM node, but still want to notify layer about event, so it can use this information to figure out correct strategy. Don't forget to pass event as last arg.


    <form onSubmit={layer.handleSubmit} />

    ^ That's all you need to do with it.


    <button onClick={layer.resetState}>

    Resets validation layer internal state.


    Here is the quick overview what's happening on data updates and form submission under the hood.

    Value update

    • onChange / onBlur handler is triggered from the DOM
    • field.filter is triggered ?->
      • if false is returned -> we're done
      • if true is returned -> continue
    • field.transformBeforeStore is triggered (if it's defined)
    • field.onChange (or props.onChange) is triggered
    • sync validation is triggered (if any) ?->
      • if no results emitted -> updating the state and we're done
      • if failed results emitted -> updating the state and we're done
      • if success results emitted ?->
        • if there is no async validation -> updating the state and we're done
        • if there is async validation -> updating the state with processing status and trigger async validation, when results are resolved -> updating the state and we're done.

    Form submission

    • layer.handleSubmit is triggered from the DOM
    • Validation layer performs sync validation of all fields (no async validations performed) ?->
      • if at least one field is invalid -> updating the state with the errors and we're done
      • if all fields are valid -> triggering handlers.onSubmit and pass object with callbacks ?->
        • callback.onSuccess should be triggered when form is successfully submitted -> resetting the layer to initial state and we're done
        • callback.onFailure should be triggered when something gone wrong, i.e. API returned errors, which should be passed to callback.onFailure -> updating the state with the errors and we're done.

    WIPs & TODOs

    Those will be figured out (sooner or later), upvote them if you need them 👍

    • Collections handling, e.g. arrays of entities (#12)
    • Refs handling, e.g. focus on first invalid input after submission (#13)

    See issues & pull requests for more details.


    It's MIT.


    npm i react-validation-layer

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