function App () {

  const storedValue = localStorage.getItem('username')

  const [value, setValue] = React.useState(storedValue || '')

  const handleChange = e => {

    const value = e.target.value

    setValue(value)

    localStorage.setItem('username', value)

  }

​

  return (

    <form>

      <label>Username</label>

      <input type="text" value={value} onChange={handleChange} />

    </form>

  )

}