Focus Management | TanStack Form 简体中文

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.

React DOM

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() {
      const InvalidInput = document.querySelector(
        '[aria-invalid="true"]',
      ) as HTMLInputElement

      InvalidInput?.focus()
    },
  })

  return (
    <form
      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}
              aria-invalid={
                !field.state.meta.isValid && field.state.meta.isTouched
              }
              onChange={(e) => field.handleChange(e.target.valueAsNumber)}
              type="number"
            />
          </label>
        )}
      />
      <div>
        <button type="submit">Submit</button>
      </div>
    </form>
  )
}

React Native

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>
  )
}