Form

'use client';
import * as React from 'react';
import { Field } from '@base-ui/react/field';
import { Form } from '@base-ui/react/form';
import { Button } from '@base-ui/react/button';
import styles from './index.module.css';

export default function ExampleForm() {
  const [errors, setErrors] = React.useState({});
  const [loading, setLoading] = React.useState(false);

  return (
    <Form
      className={styles.Form}
      errors={errors}
      onSubmit={async (event) => {
        event.preventDefault();
        const formData = new FormData(event.currentTarget);
        const value = formData.get('url') as string;

        setLoading(true);
        const response = await submitForm(value);
        const serverErrors = {
          url: response.error,
        };

        setErrors(serverErrors);
        setLoading(false);
      }}
    >
      <Field.Root name="url" className={styles.Field}>
        <Field.Label className={styles.Label}>Homepage</Field.Label>
        <Field.Control
          type="url"
          required
          defaultValue="https://example.com"
          placeholder="https://example.com"
          pattern="https?://.*"
          className={styles.Input}
        />
        <Field.Error className={styles.Error} />
      </Field.Root>
      <Button type="submit" disabled={loading} focusableWhenDisabled className={styles.Button}>
        Submit
      </Button>
    </Form>
  );
}

async function submitForm(value: string) {
  // Mimic a server response
  await new Promise((resolve) => {
    setTimeout(resolve, 1000);
  });

  try {
    const url = new URL(value);

    if (url.hostname.endsWith('example.com')) {
      return { error: 'The example domain is not allowed' };
    }
  } catch {
    return { error: 'This is not a valid URL' };
  }

  return { success: true };
}

'use client';
import * as React from 'react';
import { Field } from '@base-ui/react/field';
import { Form } from '@base-ui/react/form';
import { Button } from '@base-ui/react/button';
import styles from './index.module.css';

interface FormState {
  serverErrors?: Form.Props['errors'];
}

export default function ActionStateForm() {
  const [state, formAction, loading] = React.useActionState<FormState, FormData>(submitForm, {});

  return (
    <Form errors={state.serverErrors} action={formAction} className={styles.Form}>
      <Field.Root name="username" className={styles.Field}>
        <Field.Label className={styles.Label}>Username</Field.Label>
        <Field.Control
          type="username"
          required
          defaultValue="admin"
          placeholder="e.g. alice132"
          className={styles.Input}
        />
        <Field.Error className={styles.Error} />
      </Field.Root>
      <Button type="submit" disabled={loading} focusableWhenDisabled className={styles.Button}>
        Submit
      </Button>
    </Form>
  );
}

// Mark this as a Server Function with `'use server'` in a supporting framework like Next.js
async function submitForm(_previousState: FormState, formData: FormData) {
  // Mimic a server response
  await new Promise((resolve) => {
    setTimeout(resolve, 1000);
  });

  try {
    const username = formData.get('username') as string | null;

    if (username === 'admin') {
      return { success: false, serverErrors: { username: "'admin' is reserved for system use" } };
    }

    // 50% chance the username is taken
    const success = Math.random() > 0.5;

    if (!success) {
      return {
        serverErrors: { username: `${username} is unavailable` },
      };
    }
  } catch {
    return { serverErrors: { username: 'A server error has occurred' } };
  }

  return {};
}

'use client';
import * as React from 'react';
import { z } from 'zod';
import { Field } from '@base-ui/react/field';
import { Form } from '@base-ui/react/form';
import { Button } from '@base-ui/react/button';
import styles from './index.module.css';

const schema = z.object({
  name: z.string().min(1, 'Name is required'),
  age: z.coerce.number('Age must be a number').positive('Age must be a positive number'),
});

async function submitForm(formValues: Form.Values) {
  const result = schema.safeParse(formValues);

  if (!result.success) {
    return {
      errors: z.flattenError(result.error).fieldErrors,
    };
  }

  return {
    errors: {},
  };
}

export default function Page() {
  const [errors, setErrors] = React.useState({});

  return (
    <Form
      className={styles.Form}
      errors={errors}
      onFormSubmit={async (formValues) => {
        const response = await submitForm(formValues);
        setErrors(response.errors);
      }}
    >
      <Field.Root name="name" className={styles.Field}>
        <Field.Label className={styles.Label}>Name</Field.Label>
        <Field.Control placeholder="Enter name" className={styles.Input} />
        <Field.Error className={styles.Error} />
      </Field.Root>
      <Field.Root name="age" className={styles.Field}>
        <Field.Label className={styles.Label}>Age</Field.Label>
        <Field.Control placeholder="Enter age" className={styles.Input} />
        <Field.Error className={styles.Error} />
      </Field.Root>
      <Button type="submit" className={styles.Button}>
        Submit
      </Button>
    </Form>
  );
}