The React 19 useActionState hook is a powerful tool for creating a component state based on the result of an action, typically useful with form submissions. However, there are unclear usage patterns and some gotchas that can make it hard to work with. In this blog post, we’ll create a validated form using the hook, and we’ll see how we can handle form resets and errors with it.
The final result can be found on GithHub and tried out on Vercel. Just give the app a minute if it initially throws an application error - the database is sleeping.
Table of contents
Open Table of contents
The starting point
We have a simple form that allows us to edit a contact. The form is a React component that receives a contact prop, which is the contact we want to edit. The form has fields for the contact’s first name, last name, twitter, notes, and an avatar URL.
export default function ContactForm({ contact }: { contact: Contact }) {
return (
<form className="flex max-w-[40rem] flex-col gap-4 @container">
<div className="grip-rows-5 grid gap-2 @sm:grid-cols-[1fr_4fr] @sm:gap-4">
<span className="flex">Name</span>
<div className="flex gap-4">
<Input
defaultValue={contact?.first || undefined}
aria-label="First name"
name="first"
type="text"
placeholder="First"
/>
<Input
aria-label="Last name"
defaultValue={contact?.last || undefined}
name="last"
placeholder="Last"
type="text"
/>
</div>
<label htmlFor="avatar">Avatar URL</label>
<Input
defaultValue={contact?.avatar || undefined}
name="avatar"
placeholder="https://sessionize.com/image/example.jpg"
type="text"
/>
...Submitting the form with an action
We want to submit the form to our database using an action with the upgraded React 19 action property. This property can now be bound to a function, ƒor example a Server Function. It will receive the form data as a FormData object.
Let’s write the Server Function that will handle the form submission. We’ll call it updateContact.
'use server';
...
export async function updateContact(contactId: string, formData: FormData) {
const data = Object.fromEntries(formData);
await prisma.contact.update({
data,
where: {
id: contactId,
},
});
revalidatePath(routes.home());
redirect(routes.contactId({ contactId }));
}The function will update the contact in the database, revalidate the home page, and redirect to the contact page.
We can now bind the action to the form.
export default function ContactForm({ contact }: { contact: Contact }) {
return (
<form className="flex max-w-[40rem] flex-col gap-4 @container" action={updateContact}>
<div className="grip-rows-5 grid gap-2 @sm:grid-cols-[1fr_4fr] @sm:gap-4">
<span className="flex">Name</span>
<div className="flex gap-4">
...However, we have typescript errors, because the updateContact function requires a contactId argument. We can pass it as a hidden input in the form, or we can bind updateContact with initial arguments.
export default function ContactForm({ contact }: { contact: Contact }) {
const updateContactById = updateContact.bind(null, contact.id);
return (
<form className="flex max-w-[40rem] flex-col gap-4 @container" action={updateContactById}>
<div className="grip-rows-5 grid gap-2 @sm:grid-cols-[1fr_4fr] @sm:gap-4">
<span className="flex">Name</span>
<div className="flex gap-4">
...And this should nicely update the contact in the database when the form is submitted and redirect to the contact page.
Adding server-side validation
We want to add some validation to the form. The form here actually doesn’t require any fields to be filled. However we want to validate the avatar URL because the image won’t load if it’s not a valid URL or if its not from a valid domain. We also want to validate that the twitter handle starts with an @.
Let’s make a Zod schema for the form data. We’re also gonna export the types for the schema and the error type - we need them later.
import { z } from 'zod';
export const contactSchema = z.object({
avatar: z
.string()
.url()
.startsWith('https://sessionize.com', 'Avatar URL must be from sessionize.com')
.or(z.literal(''))
.nullable(),
first: z.string().nullable(),
last: z.string().nullable(),
notes: z.string().nullable(),
twitter: z.string().startsWith('@', 'Twitter handle must start with @').or(z.literal('')).nullable(),
});
export type ContactSchemaType = z.infer<typeof contactSchema>;
export type ContactSchemaErrorType = z.inferFlattenedErrors<typeof contactSchema>;Now we can use the schema to validate the form data in the updateContact function. If there are errors, we want to return them to from the Server Function.
'use server';
...
export async function updateContact(contactId: string, formData: FormData) {
const data = Object.fromEntries(formData);
const result = contactSchema.safeParse(data);
if (!result.success) {
return {
errors: result.error.formErrors,
};
}
await prisma.contact.update({
where: {
id: contactId,
},
});
revalidatePath(routes.home());
redirect(routes.contactId({ contactId }));
}Displaying the returned errors
Now we need to display the errors in the form. We can use the useActionState hook for that. The hook will create a state based on the result of the action.
We will pass the updateContactById function to the hook, and we will also pass an initial state with an empty errors object, utilizing the ContactSchemaErrorType type we created earlier.
And we need to make the component a client component, because we are using the useActionState hook. And we have to pass the returned, wrapped action updateContactAction to the form.
Then, we can use these errors to display them in the form. On form submission, the errors will be returned from the action and displayed in the form.
"use client"
export default function ContactForm({ contact }: { contact: Contact }) {
const updateContactById = updateContact.bind(null, contact.id);
const [state, updateContactAction] = useActionState(updateContactById, {
errors: {} as ContactSchemaErrorType,
});
return (
<form className="flex max-w-[40rem] flex-col gap-4 @container" action={updateContactAction}>
<div className="grip-rows-5 grid gap-2 @sm:grid-cols-[1fr_4fr] @sm:gap-4">
<span className="flex">Name</span>
<div className="flex gap-4">
<Input
errors={state.errors?.fieldErrors?.first}
defaultValue={contact?.first || undefined}
aria-label="First name"f
name="first"
type="text"
placeholder="First"
/>
<Input
errors={state.errors?.fieldErrors?.last}
aria-label="Last name"
defaultValue={contact?.last || undefined}
name="last"
placeholder="Last"
type="text"
/>
</div>
<label htmlFor="avatar">Avatar URL</label>
<Input
errors={state.errors?.fieldErrors?.avatar}
defaultValue={contact?.avatar || undefined}
name="avatar"
placeholder="https://sessionize.com/image/example.jpg"
type="text"
/>
...We are getting more typescript errors. That’s because the action that useActionState is wrapping is passed an additional parameter, the previous state. This is useful when we want to access the previous state of the action. However, we don’t need it in this case.
So we define this additional parameter in the updateContact function as _prevState.
We will also define a State type for pervious state.
type State = {
errors?: ContactSchemaErrorType;
};
export async function updateContact(contactId: string, _prevState: State, formData: FormData) {
const data = Object.fromEntries(formData);
...Everything should now work as expected. The form will display errors if there are any, and the contact will be updated in the database if there are no errors.
Handling form resets
We notice that when we submit the form, but it fails due to errors, the form resets. This is because in React 19, when using uncontrolled inputs and the action property, the form will reset on submission. This can be good because it mimics the MPA form submission behavior.
When it resets, it resets back to its default values, which is the contact data. If we didn’t have default values, it would be reset back to an empty form.
For our case, this is not a good user experience. We can opt out by using an onSubmit or by using controlled inputs. However, this is not a very good solution. Instead, lets return the data submitted from the Server Function. We will use the ContactSchemaType type we created earlier to type the data object in the state.
'use server';
...
type State = {
data?: ContactSchemaType;
errors?: ContactSchemaErrorType;
};
export async function updateContact(contactId: string, _prevState: State, formData: FormData) {
const data = Object.fromEntries(formData);
const result = contactSchema.safeParse(data);
if (!result.success) {
return {
data: data as ContactSchemaType,
errors: result.error.formErrors,
};
}
await prisma.contact.update({
data: result.data,
where: {
id: contactId,
},
});
revalidatePath(routes.home());
redirect(routes.contactId({ contactId }));
}And we will update the useActionState hook to use the contact as the initial values of the data, but then have it update with the data returned from the action.
"use client"
...
export default function ContactForm({ contact }: { contact: Contact }) {
const updateContactById = updateContact.bind(null, contact.id);
const [state, updateContactAction] = useActionState(updateContactById, {
data: {
avatar: contact.avatar,
first: contact.first,
last: contact.last,
notes: contact.notes,
twitter: contact.twitter,
},
errors: {} as ContactSchemaErrorType,
});
...Then, we will instead use the returned data from the action as our default form values.
return (
<form className="flex max-w-[40rem] flex-col gap-4 @container" action={updateContactAction}>
<div className="grip-rows-5 grid gap-2 @sm:grid-cols-[1fr_4fr] @sm:gap-4">
<span className="flex">Name</span>
<div className="flex gap-4">
<Input
errors={state.errors?.fieldErrors?.first}
defaultValue={state.data?.first || undefined}
aria-label="First name"
name="first"
type="text"
placeholder="First"
/>
<Input
errors={state.errors?.fieldErrors?.last}
aria-label="Last name"
defaultValue={state.data?.last || undefined}
name="last"
placeholder="Last"
type="text"
/>
...What happens now is that when the form is submitted, the data is returned from the Server Function and the form is updated with the data. If there are errors, the form is updated with the errors. This way, it feels like the form is not resetting.
Note on Progressive Enhancement
We called useActionState directly with a Server Function, and passed the returned, wrapped action directly to the form. This enables the form to submit and return errors without JavaScript, before hydration has completed. Had we used the onSubmit event, the form would not have worked without JavaScript.
This is a great example of Progressive Enhancement, where we enhance the form with JavaScript, but it still works without it. This blog post did not cover additional loading states and interactions, but these can be added to further enhance the form.
Note on the onSubmit event
The added benefit of using the action property is that the onSubmit event can be used to provide additional functionality, like client-only optimistic updates on top of the no-js base case. See example here.
Reach Hook Form as an alternative
If you are not a fan of useActionState, you can use Reach Hook Form as an alternative. It is a great library for form validation and handling, and uses controlled inputs to manage a controlled form state for you.
I have an example of that in a separate branch.
Conclusion
In this blog post, we’ve seen how to use the useActionState hook to create a validated form. We’ve also seen how to handle form resets with it. The final result can be found on GithHub and tried out on Vercel. Again, just give the app a minute if it initially throws an application error - the database is sleeping.
I hope this post has been helpful. Please let me know if you have any questions or comments, and follow me on Twitter for more updates. Happy coding! 🚀