index.tsx

import * as React from 'react'
import { createRoot } from 'react-dom/client'
import { useForm } from '@tanstack/react-form'
import { zodValidator } from '@tanstack/zod-form-adapter'
import { z } from 'zod'
import type { FieldApi } from '@tanstack/react-form'

function FieldInfo({ field }: { field: FieldApi<any, any, any, any> }) {
  return (
    <>
      {field.state.meta.isTouched && field.state.meta.errors.length ? (
        <em>{field.state.meta.errors.join(',')}</em>
      ) : null}
      {field.state.meta.isValidating ? 'Validating...' : null}
    </>
  )
}

const userSchema = z.object({
  firstName: z.string().refine((val) => val !== 'John', {
    message: '[Form] First name cannot be John',
  }),
  lastName: z.string().min(3, '[Form] Last name must be at least 3 characters'),
})

type User = z.infer<typeof userSchema>

export default function App() {
  const form = useForm({
    defaultValues: {
      firstName: '',
      lastName: '',
    } as User,
    onSubmit: async ({ value }) => {
      // Do something with form data
      console.log(value)
    },
    // Add a validator to support Zod usage in Form and Field
    validatorAdapter: zodValidator(),
    validators: {
      onChange: userSchema,
    },
  })

  return (
    <div>
      <h1>Zod Form Example</h1>
      <form
        onSubmit={(e) => {
          e.preventDefault()
          e.stopPropagation()
          form.handleSubmit()
        }}
      >
        <div>
          {/* A type-safe field component*/}
          <form.Field
            name="firstName"
            validators={{
              onChange: z
                .string()
                .min(3, '[Field] First name must be at least 3 characters'),
              onChangeAsyncDebounceMs: 500,
              onChangeAsync: z.string().refine(
                async (value) => {
                  await new Promise((resolve) => setTimeout(resolve, 1000))
                  return !value.includes('error')
                },
                {
                  message: "[Field] No 'error' allowed in first name",
                },
              ),
            }}
            children={(field) => {
              // Avoid hasty abstractions. Render props are great!
              return (
                <>
                  <label htmlFor={field.name}>First Name:</label>
                  <input
                    id={field.name}
                    name={field.name}
                    value={field.state.value}
                    onBlur={field.handleBlur}
                    onChange={(e) => field.handleChange(e.target.value)}
                  />
                  <FieldInfo field={field} />
                </>
              )
            }}
          />
        </div>
        <div>
          <form.Field
            name="lastName"
            children={(field) => (
              <>
                <label htmlFor={field.name}>Last Name:</label>
                <input
                  id={field.name}
                  name={field.name}
                  value={field.state.value}
                  onBlur={field.handleBlur}
                  onChange={(e) => field.handleChange(e.target.value)}
                />
                <FieldInfo field={field} />
              </>
            )}
          />
        </div>
        <form.Subscribe
          selector={(state) => [state.canSubmit, state.isSubmitting]}
          children={([canSubmit, isSubmitting]) => (
            <button type="submit" disabled={!canSubmit}>
              {isSubmitting ? '...' : 'Submit'}
            </button>
          )}
        />
      </form>
    </div>
  )
}

const rootElement = document.getElementById('root')!

createRoot(rootElement).render(
  <React.StrictMode>
    <App />
  </React.StrictMode>,
)