function App () {

  const [data, setData] = React.useState({

    email: '',

    password: ''

  })

  const handleChange = paramName => event => {

    setData(prevData => ({

      email: prevData.email,

      password: prevData.password,

      [paramName]: event.target.value

    }))

  }

  const handleSubmit = (event) => {

    event.preventDefault()

    console.log('Submit', data)

  }

  const isDisabled = !data.email || !data.password

​

  return (

    <form onSubmit={handleSubmit}>

      <input type="text" placeholder="E-mail" value={data.email} onChange={handleChange('email')} />

      <input type="password" placeholder="Password" value={data.password} onChange={handleChange('password')} />

      <button type="submit" disabled={isDisabled}>Submit</button>

    </form>

  )