function App() {
  const [numbers, setNumbers] = React.useState([0, 1, 2, 3]);
  console.log("rendering...");
  return (
    <div className="App">
      {numbers.map(number => (
        <p>{number}</p>
      ))}
      <input
        type="text"
        value={numbers[0].toString()}
        onChange={newText => {
          let old = numbers;
          old[0] = 1);
          setNumbers(old);
        }}
      />
    </div>
  );
}