File: tanstack-start.md | Updated: 11/15/2025
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React Example: Tanstack Start
==============================================================================================================================================================================================================================================================================================================================================================================================================================
Code ExplorerCode
Interactive SandboxSandbox
public
src
routes
__root.tsx
index.tsx
utils
routeTree.gen.ts
router.tsx
.gitignore
README.md
package.json
tsconfig.json
vite.config.ts
tsx
import { createFileRoute } from '@tanstack/react-router'
import { mergeForm, useForm, useTransform } from '@tanstack/react-form-start'
import { useStore } from '@tanstack/react-store'
import { getFormDataFromServer, handleForm } from 'src/utils/form'
import { formOpts } from 'src/utils/form-isomorphic'
export const Route = createFileRoute('/')({
component: Home,
loader: async () => ({
state: await getFormDataFromServer(),
}),
})
function Home() {
const { state } = Route.useLoaderData()
const form = useForm({
...formOpts,
transform: useTransform((baseForm) => mergeForm(baseForm, state), [state]),
})
const formErrors = useStore(form.store, (formState) => formState.errors)
return (
<form action={handleForm.url} method="post" encType={'multipart/form-data'}>
{formErrors.map((error) => (
<p key={error as never as string}>{error}</p>
))}
<form.Field
name="age"
validators={{
onChange: ({ value }) =>
value < 8 ? 'Client validation: You must be at least 8' : undefined,
}}
>
{(field) => {
return (
<div>
<input
name="age"
type="number"
value={field.state.value}
onChange={(e) => field.handleChange(e.target.valueAsNumber)}
/>
{field.state.meta.errors.map((error) => (
<p key={error as string}>{error}</p>
))}
</div>
)
}}
</form.Field>
<form.Subscribe
selector={(formState) => [formState.canSubmit, formState.isSubmitting]}
>
{([canSubmit, isSubmitting]) => (
<button type="submit" disabled={!canSubmit}>
{isSubmitting ? '...' : 'Submit'}
</button>
)}
</form.Subscribe>
</form>
)
}
import { createFileRoute } from '@tanstack/react-router'
import { mergeForm, useForm, useTransform } from '@tanstack/react-form-start'
import { useStore } from '@tanstack/react-store'
import { getFormDataFromServer, handleForm } from 'src/utils/form'
import { formOpts } from 'src/utils/form-isomorphic'
export const Route = createFileRoute('/')({
component: Home,
loader: async () => ({
state: await getFormDataFromServer(),
}),
})
function Home() {
const { state } = Route.useLoaderData()
const form = useForm({
...formOpts,
transform: useTransform((baseForm) => mergeForm(baseForm, state), [state]),
})
const formErrors = useStore(form.store, (formState) => formState.errors)
return (
<form action={handleForm.url} method="post" encType={'multipart/form-data'}>
{formErrors.map((error) => (
<p key={error as never as string}>{error}</p>
))}
<form.Field
name="age"
validators={{
onChange: ({ value }) =>
value < 8 ? 'Client validation: You must be at least 8' : undefined,
}}
>
{(field) => {
return (
<div>
<input
name="age"
type="number"
value={field.state.value}
onChange={(e) => field.handleChange(e.target.valueAsNumber)}
/>
{field.state.meta.errors.map((error) => (
<p key={error as string}>{error}</p>
))}
</div>
)
}}
</form.Field>
<form.Subscribe
selector={(formState) => [formState.canSubmit, formState.isSubmitting]}
>
{([canSubmit, isSubmitting]) => (
<button type="submit" disabled={!canSubmit}>
{isSubmitting ? '...' : 'Submit'}
</button>
)}
</form.Subscribe>
</form>
)
}
