In some instances, you may want to focus the first input with an error.
Because TanStack Form intentionally does not have insights into your markup, we cannot add a built-in focus management feature.
However, you can easily add this feature into your application without this hypothetical built-in feature.
import { useForm } from '@tanstack/react-form'
import { z } from 'zod'
export default function App() {
const form = useForm({
defaultValues: { age: 0 },
validators: {
onChange: z.object({
age: z.number().min(12),
}),
},
onSubmit() {
alert('Submitted!')
},
onSubmitInvalid({ formApi }) {
// This can be extracted to a function that takes the form ID and `formAPI` as arguments
const errorMap = formApi.state.errorMap.onChange!
const inputs = Array.from(
// Must match the selector used in your form
document.querySelectorAll('#myform input'),
) as HTMLInputElement[]
let firstInput: HTMLInputElement | undefined
for (const input of inputs) {
if (!!errorMap[input.name]) {
firstInput = input
break
}
}
firstInput?.focus()
},
})
return (
// The `id` here is used to isolate the focus management from the rest of the page
<form
id="myform"
onSubmit={(e) => {
e.preventDefault()
e.stopPropagation()
void form.handleSubmit()
}}
>
<form.Field
name="age"
children={(field) => (
<label>
Age
<input
name={field.name}
value={field.state.value}
onChange={(e) => field.handleChange(e.target.valueAsNumber)}
type="number"
/>
</label>
)}
/>
<div>
<button type="submit">Submit</button>
</div>
</form>
)
}
import { useForm } from '@tanstack/react-form'
import { z } from 'zod'
export default function App() {
const form = useForm({
defaultValues: { age: 0 },
validators: {
onChange: z.object({
age: z.number().min(12),
}),
},
onSubmit() {
alert('Submitted!')
},
onSubmitInvalid({ formApi }) {
// This can be extracted to a function that takes the form ID and `formAPI` as arguments
const errorMap = formApi.state.errorMap.onChange!
const inputs = Array.from(
// Must match the selector used in your form
document.querySelectorAll('#myform input'),
) as HTMLInputElement[]
let firstInput: HTMLInputElement | undefined
for (const input of inputs) {
if (!!errorMap[input.name]) {
firstInput = input
break
}
}
firstInput?.focus()
},
})
return (
// The `id` here is used to isolate the focus management from the rest of the page
<form
id="myform"
onSubmit={(e) => {
e.preventDefault()
e.stopPropagation()
void form.handleSubmit()
}}
>
<form.Field
name="age"
children={(field) => (
<label>
Age
<input
name={field.name}
value={field.state.value}
onChange={(e) => field.handleChange(e.target.valueAsNumber)}
type="number"
/>
</label>
)}
/>
<div>
<button type="submit">Submit</button>
</div>
</form>
)
}
Because React Native doesn't have access to the DOM's querySelectorAll API, we need to manually manage the element list of the inputs. This allows us to focus the first input with an error:
import { useRef } from 'react'
import { Text, View, TextInput, Button, Alert } from 'react-native'
import { useForm } from '@tanstack/react-form'
import { z } from 'zod'
export default function App() {
// This can be extracted to a hook that returns the `fields` ref, a `focusFirstField` function, and a `addField` function
const fields = useRef([] as Array<{ input: TextInput; name: string }>)
const form = useForm({
defaultValues: { age: 0 },
validators: {
onChange: z.object({
age: z.number().min(12),
}),
},
onSubmit() {
Alert.alert('Submitted!')
},
onSubmitInvalid({ formApi }) {
const errorMap = formApi.state.errorMap.onChange
const inputs = fields.current
let firstInput
for (const input of inputs) {
if (!input || !input.input) continue
if (!!errorMap[input.name]) {
firstInput = input.input
break
}
}
firstInput?.focus()
},
})
return (
<View style={{ padding: 16 }}>
<form.Field
name="age"
children={(field) => (
<View style={{ marginVertical: 16 }}>
<Text>Age</Text>
<TextInput
keyboardType="numeric"
ref={(input) => {
// fields.current needs to be manually incremented so that we know what fields are rendered or not and in what order
fields.current[0] = { input, name: field.name }
}}
style={{
borderWidth: 1,
borderColor: '#999999',
borderRadius: 4,
marginTop: 8,
padding: 8,
}}
onChangeText={(val) => field.handleChange(Number(val))}
value={field.state.value}
/>
</View>
)}
/>
<Button title="Submit" onPress={form.handleSubmit} />
</View>
)
}
import { useRef } from 'react'
import { Text, View, TextInput, Button, Alert } from 'react-native'
import { useForm } from '@tanstack/react-form'
import { z } from 'zod'
export default function App() {
// This can be extracted to a hook that returns the `fields` ref, a `focusFirstField` function, and a `addField` function
const fields = useRef([] as Array<{ input: TextInput; name: string }>)
const form = useForm({
defaultValues: { age: 0 },
validators: {
onChange: z.object({
age: z.number().min(12),
}),
},
onSubmit() {
Alert.alert('Submitted!')
},
onSubmitInvalid({ formApi }) {
const errorMap = formApi.state.errorMap.onChange
const inputs = fields.current
let firstInput
for (const input of inputs) {
if (!input || !input.input) continue
if (!!errorMap[input.name]) {
firstInput = input.input
break
}
}
firstInput?.focus()
},
})
return (
<View style={{ padding: 16 }}>
<form.Field
name="age"
children={(field) => (
<View style={{ marginVertical: 16 }}>
<Text>Age</Text>
<TextInput
keyboardType="numeric"
ref={(input) => {
// fields.current needs to be manually incremented so that we know what fields are rendered or not and in what order
fields.current[0] = { input, name: field.name }
}}
style={{
borderWidth: 1,
borderColor: '#999999',
borderRadius: 4,
marginTop: 8,
padding: 8,
}}
onChangeText={(val) => field.handleChange(Number(val))}
value={field.state.value}
/>
</View>
)}
/>
<Button title="Submit" onPress={form.handleSubmit} />
</View>
)
}
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