Sveltik

Forms in Svelte, inspired by Formik.

<script>
    import { Sveltik, Form, Field, ErrorMessage } from 'sveltik'

    let initialValues = {
        email: '',
        password: '',
    }

    let validate = values => {
        const errors = {}
        if (!values.email) {
            errors.email = 'Required'
        } else if (!/^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,}$/i.test(values.email)) {
            errors.email = 'Invalid email address'
        }
        return errors
    }

    let onSubmit = (values, { setSubmitting }) => {
        setTimeout(() => {
            alert(JSON.stringify(values, null, 2))
            setSubmitting(false)
        }, 400)
    }
</script>

<Sveltik {initialValues} {validate} {onSubmit} let:isSubmitting>
    <Form>
        <Field type="email" name="email" />
        <ErrorMessage name="email" as="div" />
        <Field type="password" name="password" />
        <ErrorMessage name="password" as="div" />
        <button type="submit" disabled={isSubmitting}>Submit</button>
    </Form>
</Sveltik>

<Sveltik />

<Sveltik /> is a component for rendering forms. It is largely a port of Formik to Svelte and broadly follows the same API. It uses a let:props pattern which is generally similar to the render prop pattern in React.

Example

Open in REPL

<script>
    import { Sveltik } from 'sveltik'
</script>

<div>
    <h1>My Form</h1>
    <Sveltik
        initialValues={{ name: 'jared' }}
        onSubmit={(values, actions) => {
            setTimeout(() => {
                alert(JSON.stringify(values, null, 2))
                actions.setSubmitting(false)
            }, 1000)
        }}
        let:props
    >
        <form on:submit|preventDefault={props.handleSubmit}>
            <input
                type="text"
                on:input={props.handleInput}
                on:blur={props.handleBlur}
                value={props.values.name}
                name="name"
            />
            {#if props.errors.name}
                <div id="feedback">{props.errors.name}</div>
            {/if}
            <button type="submit">Submit</button>
        </form>
    </Sveltik>
</div>

Props

• enableReinitialize?: boolean
• initialErrors?: SveltikErrors<Values>
• initialStatus?: any
• initialTouched?: SveltikTouched<Values>
• initialValues: Values
• initialWarnings?: SveltikWarnings<Values>
• onReset?: (values: Values, sveltikBag: SveltikBag) => void
• onSubmit: (values: Values, sveltikBag: SveltikBag) => void | Promise<any>
• validate?: (values: Values, sveltikBag: SveltikBag) => SveltikErrors<Values>
• validateOnBlur?: boolean
• validateOnChange?: boolean
• validateOnMount?: boolean

let:props

• let:props: SveltikProps
• let:isDirty: boolean
• let:errors: { [field: string]: string }
• let:handleBlur: (e: HTMLBlurEvent) => void
• let:handleInput: (e: HTMLInputEvent) => void
• let:handleReset: () => void
• let:handleSubmit: (e: HTMLFormEvent) => void
• let:isSubmitting: boolean
• let:isValid: boolean
• let:isValidating: boolean
• let:resetForm: (nextInitialState?: SveltikState<Values>) => void
• let:scrollFirstErrorIntoView: () => void
• let:setErrors: (fields: { [field: string]: string }) => void
• let:setFieldError: (field: string, errorMsg: string) => void
• let:setFieldTouched: (field: string, isTouched?: boolean, shouldValidate?: boolean) => void
• let:setFieldValue: (field: string, value: any, shouldValidate?: boolean) => void
• let:setFieldWarning: (field: string, warning: string) => void
• let:setStatus: (status?: any) => void
• let:setSubmitting: (isSubmitting: boolean) => void
• let:setTouched: (fields: { [field: string]: boolean }, shouldValidate?: boolean) => void
• let:setValues: (fields: { [field: string]: any }, shouldValidate?: boolean) => void
• let:setWarnings: (fields: { [field: string]: string }) => void
• let:status: any
• let:submitAttemptCount: number
• let:submitFailure: () => void
• let:submitFailureCount: number
• let:submitForm: () => Promise
• let:submitSuccess: () => void
• let:submitSuccessCount: number
• let:touched: { [field: string]: boolean }
• let:values: { [field: string]: any }
• let:validateForm: (values?: any) => void
• let:validateField: (field: string) => void
• let:warnings: { [field: string]: string }

Reference

Props

enableReinitialize?: boolean

Default is false. Control whether Sveltik should reset the form if initialValues changes (using deep equality).

initialErrors?: SveltikErrors<Values>

Initial field errors of the form, Sveltik will make these values available to render methods component as errors.

initialStatus?: any

An arbitrary value for the initial status of the form. If the form is reset, this value will be restored.

initialTouched?: SveltikTouched<Values>

Initial visitied fields of the form, Sveltik will make these values available to render methods component as touched.

initialValues: Values

Initial field values of the form, Sveltik will make these values available to render methods component as values.

Even if your form is empty by default, you must initialize all fields with initial values.

onReset?: (values: Values, sveltikBag: SveltikBag) => void

Your optional form reset handler. It is passed your forms values and the "SveltikBag".

onSubmit: (values: Values, sveltikBag: SveltikBag) => void | Promise<any>

Your form submission handler. It is passed your forms values and the "SveltikBag", which includes an object containing a subset of the injected props and methods (i.e. all the methods with names that start with set<Thing> + resetForm) and any props that were passed to the wrapped component. If onSubmit returns a promise, rejection automatically calls submitFailure and resolution automatically calls submitSuccess.

validate?: (values: Values) => SveltikErrors<Values>

Validate the form's values with function. Synchronous and return an errors object.

validateOnBlur?: boolean

Default is true. Use this option to run validations on blur events. More specifically, when either handleBlur, setFieldTouched, or setTouched are called.

validateOnChange?: boolean

Default is true. Use this option to tell Sveltik to run validations on change events and change-related methods. More specifically, when either handleInput, setFieldValue, or setValues are called.

validateOnMount?: boolean

Default is false. Use this option to tell Sveltik to run validations when the <Sveltik /> component mounts and/or initialValues change.

let:props

All of these props are exposed individually as well as a master let:props prop which is an object of all available props.

let:isDirty: boolean

Returns true if values are not deeply equal from initial values, false otherwise. dirty is a readonly computed property and should not be mutated directly.

let:errors: { [field: string]: string }

Form validation errors. Should match the shape of your form's values defined in initialValues.

let:handleBlur: (e: HTMLBlurEvent) => void

onBlur event handler. Useful for when you need to track whether an input has been touched or not. This should be passed to <input on:blur={handleBlur} ... />

let:handleInput: (e: HTMLInputEvent) => void

General input change event handler. This will update the values[key] where key is the event-emitting input's name attribute. If the name attribute is not present, handleInput will look for an input's id attribute. Note: "input" here means all HTML inputs.

let:handleReset: () => void

Reset handler. Will reset the form to its initial state. This should be passed to <button on:click={handleReset}>...</button>

let:handleSubmit: (e: HTMLFormEvent) => void

Submit handler. This should be passed to <form on:submit|preventDefault={props.handleSubmit}>...</form>.

let:isSubmitting: boolean

Submitting state of the form. Returns true if submission is in progress and false otherwise.

let:isValid: boolean

Returns true if there are no errors (i.e. the errors object is empty) and false otherwise.

let:isValidating: boolean

Returns true if Sveltik is running validation during submission, or by calling validateForm directly false otherwise.

let:resetForm: (nextInitialState?: SveltikState<Values>) => void

Imperatively reset the form. If nextInitialState is specified, Sveltik will set this state as the new "initial state" and use the related values of nextInitialState to update the form's initialValues as well as initialTouched, initialStatus, initialErrors. This is useful for altering the initial state (i.e. "base") of the form after changes have been made. If nextInitialState is not defined, then Sveltik will reset state to the original initial state.

let:scrollFirstErrorIntoView: () => void

Scroll the first <ScrollMarker /> with an error into view. First is calculated by the vertical distance from the top of the document.

let:setErrors: (fields: { [field: string]: string }) => void

Set errors imperatively.

let:setFieldError: (field: string, errorMsg: string) => void

Set the error message of a field imperatively. field should match the key of errors you wish to update. Useful for creating custom input error handlers.

let:setFieldTouched: (field: string, isTouched?: boolean, shouldValidate?: boolean) => void

Set the touched state of a field imperatively. field should match the key of touched you wish to update. Useful for creating custom input blur handlers. Calling this method will trigger validation to run if validateOnBlur is set to true (which it is by default). isTouched defaults to true if not specified. You can also explicitly prevent/skip validation by passing a third argument as false.

let:setFieldValue: (field: string, value: any, shouldValidate?: boolean) => void

Set the value of a field imperatively. field should match the key of values you wish to update. Useful for creating custom input change handlers. Calling this will trigger validation to run if validateOnChange is set to true (which it is by default). You can also explicitly prevent/skip validation by passing a third argument as false.

let:setFieldWarning: (field: string, warning: string) => void

Set the warning of a field imperatively. field should match the key of warnings you wish to update.

let:setStatus: (status?: any) => void

Set a top-level status to anything you want imperatively. Useful for controlling arbitrary top-level state related to your form. For example, you can use it to pass API responses back into your component in handleSubmit.

let:setSubmitting: (isSubmitting: boolean) => void

Set isSubmitting imperatively. You would call it with setSubmitting(false) in your onSubmit handler to finish the cycle.

let:setTouched: (fields: { [field: string]: boolean }, shouldValidate?: boolean) => void

Set touched imperatively. Calling this will trigger validation to run if validateOnBlur is set to true (which it is by default). You can also explicitly prevent/skip validation by passing a second argument as false.

let:setValues: (fields: { [field: string]: any }, shouldValidate?: boolean) => void

Set values imperatively. Calling this will trigger validation to run if validateOnChange is set to true (which it is by default). You can also explicitly prevent/skip validation by passing a second argument as false.

let:setWarnings: (fields: { [field: string]: string }) => void

Set warnings imperatively.

let:status: any

A top-level status object that you can use to represent form state that can't otherwise be expressed/stored with other methods. This is useful for capturing and passing through API responses to your inner component. status should only be modified by calling setStatus.

let:submitAttemptCount: number

Number of times user tried to submit the form. Increases when handleSubmit is called, resets after calling handleReset.

let:submitFailure: () => void

Increment submitFailureCount by 1 and calls setSubmitting(false).

let:submitFailureCount: number

Number of failed form submissions. Increases when submitFailure is called, resets after calling handleReset.

let:submitForm: () => Promise

Trigger a form submission. The promise will be rejected if form is invalid.

let:submitSuccess: () => void

Increment submitSuccessCount by 1 and calls setSubmitting(false).

let:submitSuccessCount: number

Number of successful form submissions. Increases when submitSuccess is called, resets after calling handleReset.

let:touched: { [field: string]: boolean }

Touched fields. Each key corresponds to a field that has been touched/visited.

let:values: { [field: string]: any }

Your form's values.

let:validateForm: (values?: any) => void

Imperatively call validate. You can optionally pass values to validate against and this modify Sveltik state accordingly, otherwise this will use the current values of the form.

let:validateField: (field: string) => void

Imperatively call field's validate function if specified for given field. Sveltik will use the current field value.

let:warnings: { [field: string]: string }

Form warnings. Should match the shape of your form's values defined in initialValues.

Differences with Formik

• Validation is synchronous
• Includes support for field warnings with warnings, setWarnings, setFieldWarning
• Includes support for submission success/failure with submitSuccess and submitFailure helpers
• Tracks submitAttemptCount, submitFailureCount and submitSuccessCount instead of only submitCount
• If onSubmit returns a promise, it's rejection calls submitFailure and it's resolution calls submitSuccess
• Does not (yet) implement Yup or validateSchema

<Field />

<Field /> will automagically hook up inputs to Sveltik. It uses the name attribute to match up with Sveltik state. With no options passed, <Field /> will default to an HTML <input /> element.

Example

Open in REPL

MyInput.svelte

<script>
    export let field
    export let props
</script>

<input {...field} {...props} on:input={field.handleInput} on:blur={field.handleBlur} />

App.svelte

<script>
    import { Sveltik, Form, Field } from 'sveltik'
    import MyInput from './MyInput.svelte'
</script>

<div>
    <h1>My Form</h1>
    <Sveltik
        initialValues={{ email: '', color: 'red', firstName: '', lastName: '' }}
        onSubmit={(values, actions) => {
            setTimeout(() => {
                alert(JSON.stringify(values, null, 2))
                actions.setSubmitting(false)
            }, 1000)
        }}
    >
        <Form>
            <Field type="email" name="email" placeholder="Email" />
            <Field as="select" name="color">
                <option value="red">Red</option>
                <option value="green">Green</option>
                <option value="blue">Blue</option>
            </Field>

            <Field name="firstName" let:field let:meta>
                <div>
                    <input
                        type="text"
                        placeholder="Jon"
                        {...field}
                        on:input={field.handleInput}
                        on:blur={field.handleBlur}
                    />
                    {#if meta.touched && meta.error}
                        <div className="error">{meta.error}</div>
                    {/if}
                </div>
            </Field>

            <Field name="lastName" placeholder="Doe" as={MyInput} />
            <button type="submit">Submit</button>
        </Form>
    </Sveltik>
</div>

Props

• as?: string | Component
• name: string
• validate?: (value: any) => undefined | string

let:props

• let:field: FieldInputProps
• let:form: SveltikBag
• let:meta: FieldMetaProps

Reference

Props

as?: string | Component

Either a Svelte component or the name of an HTML element to render. Supports the following:

• input
• select
• textarea

Svelte components must export let the props that they expect to be passed. The available props are match the let:props (see below). Also is passed an additional prop props which contains all additional props passed to <Field />.

name: string

A field's name in Sveltik state. Required.

validate?: (value: any) => undefined | string

You can run independent field-level validations by passing a function to the validate prop. The function will respect the validateOnBlur and validateOnChange config/props specified in the <Field>'s parent <Sveltik>.

If invalid, return a string containing the error message or return undefined.

let:props

let:field: FieldInputProps

An object that contains:

• name: string - The name of the field
• value: any - The value of the field
• handleInput: (e: HTMLInputEvent) => void - Input handler to be bound with on:input
• handleBlur: (e: HTMLBlurEvent) => void - Blur handler to be bound with on:blur

let:form: SveltikBag

let:meta: FieldMetaProps

An object that contains:

• initialError?: string - The field's initial error if the field is present in initialErrors
• initialTouched?: boolean - The field's initial value if the field is present in initialTouched
• initialValue?: any - The field's initial value if the field is given a value in initialValues
• initialWarning?: string - The field's initial warning if the field is given a value in initialWarnings
• error?: string - The field's error message
• touched?: boolean - Whether the field has been visited
• value?: any - The field's value
• warning?: string - The field's warning message

Differences with Formik

• Validation is synchronous
• Event handlers must be set implictly with on:input, on:blur instead of spread attributes.
• Nested field names (paths) are not supported.

<Form />

Form is a small wrapper around an HTML <form> element that automatically hooks into Sveltik's handleSubmit and handleReset. All other props are passed directly through to the DOM node.

// so...
<Form />

// is identical to this...
<form on:reset={props.handleReset} on:submit={props.handleSubmit} {...props} />

<ErrorMessage />

<ErrorMessage /> is a component that renders the error message of a given field if that field has been visited (i.e.touched[name] === true) (and there is an error message present). It expects that all error messages are stored for a given field as a string.

Props

• as?: string | Component
• name: string

let:props

• let:msg: string

Reference

Props

as?: string | Component

Either a Svelte component or the name of an HTML element to render. If not specified, <ErrorMessage /> will just return a string.

Svelte components must export let the props that they expect to be passed. The available props are match the let:props (see below). Also is passed an additional prop props which contains all additional props passed to <ErrorMessage />.

name: string

A field's name in Sveltik state. Required.

let:props

let:msg: string

A field's error message.

Differences with Formik

• Nested field names (paths) are not supported.
• Uses as prop instead of component for consistency with <Field />

<ScrollMarker />

<ScrollMarker /> marks the DOM scroll position of a form element in the document. It renders a zero-height div. Useful for scrolling to the first field with an error.

Props

• name: string

Reference

Props

name: string

A field's name in Sveltik state. Required.