React Example: Array

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import * as React from 'react'
import { createRoot } from 'react-dom/client'

import { TanStackDevtools } from '@tanstack/react-devtools'
import { formDevtoolsPlugin } from '@tanstack/react-form-devtools'
import { useForm } from '@tanstack/react-form'

interface Person {
  name: string
  age: number
}

const defaultPeople: { people: Array<Person> } = { people: [] }

function App() {
  const form = useForm({
    defaultValues: defaultPeople,
    onSubmit({ value }) {
      alert(JSON.stringify(value))
    },
  })

  return (
    <div>
      <form
        onSubmit={(e) => {
          e.preventDefault()
          e.stopPropagation()
          form.handleSubmit()
        }}
      >
        <form.Field name="people" mode="array">
          {(field) => {
            return (
              <div>
                {field.state.value.map((_, i) => {
                  return (
                    <form.Field key={i} name={`people[${i}].name`}>
                      {(subField) => {
                        return (
                          <div>
                            <label>
                              <div>Name for person {i}</div>
                              <input
                                value={subField.state.value}
                                onChange={(e) =>
                                  subField.handleChange(e.target.value)
                                }
                              />
                            </label>
                          </div>
                        )
                      }}
                    </form.Field>
                  )
                })}
                <button
                  onClick={() => field.pushValue({ name: '', age: 0 })}
                  type="button"
                >
                  Add person
                </button>
              </div>
            )
          }}
        </form.Field>
        <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 />

    <TanStackDevtools
      config={{ hideUntilHover: true }}
      plugins={[formDevtoolsPlugin()]}
    />
  </React.StrictMode>,
)