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formState

State of the form

formState: Object

This object contains information about the entire form state. It helps you to keep on track with the user's interaction with your form application.

Return

NameTypeDescription
isDirtyboolean

Set to true after the user modifies any of the inputs.

  • 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.

  • File typed input will need to be managed at the app level due to the ability to cancel file selection and FileList object.

dirtyFieldsobject

An object with the user-modified fields. Make sure to provide all inputs' defaultValues via useForm, so the library can compare against the defaultValues.

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.
isSubmittedbooleanSet to true after the form is submitted. Will remain true until the reset method is invoked.
isSubmitSuccessfulboolean

Indicate the form was successfully submitted without any Promise rejection or Error been thrown within the handleSubmit callback.

isSubmittingbooleantrue if the form is currently being submitted. false otherwise.
submitCountnumberNumber of times the form was submitted.
isValidboolean
Set to true if the form doesn't have any errors.

Note: isValid is affected by mode at useForm. This state is only applicable with onChange, onTouched, and onBlur mode.

isValidatingbooleanSet to true during validation.
errorsobjectAn object with field errors. There is also an ErrorMessage component to retrieve error message easily.

Rules

  • formState is wrapped with a Proxy to improve render performance and skip extra logic if specific state is not subscribed to. Therefore make sure you invoke or read it before a render in order to enable the state update.

  • formState is updated in batch. If you want to subscribe to formState via useEffect, make sure that you place the entire formState in the optional array.

    useEffect(() => {
  if (formState.errors.firstName) {
    // do the your logic here
  }
}, [formState]); // ✅ 
// ❌ formState.errors will not trigger the useEffect        

    import React from "react";
import { useForm } from "react-hook-form";

export default function App () {
  const {
    register,
    handleSubmit,
    formState
  } = useForm();

  const onSubmit = (data) => console.log(data);

  React.useEffect(() => {
    console.log("touchedFields", formState.touchedFields);
  },[formState]); // use entire formState object as optional array arg in useEffect, not individual properties of it


  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <input {...register("test")} />
      <input type="submit" />
    </form>
  );
};

  • Pay attention to the logical operator when subscription to formState.

    // ❌ formState.isValid is accessed conditionally, 
// so the Proxy does not subscribe to changes of that state
return <button disabled={!formState.isDirty || !formState.isValid} />;
  
// ✅ read all formState values to subscribe to changes
const { isDirty, isValid } = formState;
return <button disabled={!isDirty || !isValid} />;

Examples

CodeSandbox 
import React from "react";
import { useForm } from "react-hook-form";

export default function App() {
  const {
    register,
    handleSubmit,
    // Read the formState before render to subscribe the form state through the Proxy
    formState: { errors, isDirty, isSubmitting, touchedFields, submitCount },
  } = useForm();
  const onSubmit = (data: FormInputs) => console.log(data);

  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <input {...register("test")} />
      <input type="submit" />
    </form>
  );
}

Video

The following video will explain in detail different form states.

Thank you for your support

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