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useFormState

Subscribe to form state update

</> useFormState: ({ control: Control }) => FormState

This custom hook allows you to subscribe to each form state, and isolate the re-render at the custom hook level. It has its scope in terms of form state subscription, so it would not affect other useFormState and useForm. Using this hook can reduce the re-render impact on large and complex form application.

Props

NameTypeDescription
controlObjectcontrol object provided by useForm. It's optional if you are using FormProvider.
namestring | string[] Provide a single input name, an array of them, or subscribe to all inputs' formState update.
disabledboolean = falseOption to disable the subscription.
exactboolean = falseThis prop will enable an exact match for input name subscriptions.

Return

NameTypeDescription
isDirtybooleanSet to true after the user modifies any of the inputs.
  • Important: make sure to provide all inputs' defaultValues at the useForm, so hook form can have a single source of truth to compare whether the form is dirty.
    const {
      formState: { isDirty, dirtyFields },
      setValue
    } = useForm({ defaultValues: { test: "" } })
    

    // isDirty: true ✅
    setValue('test', 'change')
    

    // isDirty: false because there getValues() === defaultValues ❌
    setValue('test', '')
  • File typed input will need to be managed at the app level due to the ability to cancel file selection and FileList object.
  • Do not support custom object, Class or File object.
dirtyFieldsobjectAn object with the user-modified fields. Make sure to provide all inputs' defaultValues via useForm, so the library can compare against the defaultValues.
  • Important: make sure to provide defaultValues at the useForm, so hook form can have a single source of truth to compare each field's dirtiness.
  • Dirty fields will not represent as isDirty formState, because dirty fields are marked field dirty at field level rather the entire form. If you want to determine the entire form state use isDirty instead.
touchedFieldsobjectAn object containing all the inputs the user has interacted with.
defaultValuesobjectThe value which has been set at useForm's defaultValues or updated defaultValues via reset API.
isSubmittedbooleanSet to true after the form is submitted. Will remain true until the reset method is invoked.
isSubmitSuccessfulbooleanIndicate the form was successfully submitted without any runtime error.
isSubmittingbooleantrue if the form is currently being submitted. false otherwise.
isLoadingbooleantrue if the form is currently loading async default values.
  • Important: this prop is only applicable to async defaultValues
    const {
      formState: { isLoading }
    } = useForm({
      defaultValues: async () => await fetch('/api')
    })
submitCountnumberNumber of times the form was submitted.
isValidbooleanSet to true if the form doesn't have any errors.
  • setError has no effect on isValid formState, isValid will always derived via the entire form validation result.
isValidatingbooleanSet to true during validation.
validatingFieldsbooleanCapture fields which are getting async validation.
errorsobjectAn object with field errors. There is also an ErrorMessage component to retrieve error message easily.
disabledbooleanSet to true if the form is disabled via the disabled prop in useForm.
RULES

Returned formState is wrapped with Proxy to improve render performance and skip extra computation if specific state is not subscribed, so make sure you deconstruct or read it before render in order to enable the subscription.

const { isDirty } = useFormState() // ✅
const formState = useFormState() // ❌ should deconstruct the formState

Examples

CodeSandbox JS
import { useForm, useFormState } from "react-hook-form"


function Child({ control }) {
  const { dirtyFields } = useFormState({ control })


  return dirtyFields.firstName ? <p>Field is dirty.</p> : null
}


export default function App() {
  const { register, handleSubmit, control } = useForm({
    defaultValues: {
      firstName: "firstName",
    },
  })
  const onSubmit = (data) => console.log(data)


  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <input {...register("firstName")} placeholder="First Name" />
      <Child control={control} />


      <input type="submit" />
    </form>
  )
}

Thank you for your support

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