Why the display attr only change once when i click the button, it will not work afterwards

```
import React, { useState } from 'react';

function App() {
const [isShow, setIsShow] = useState(true);
const toggle = () => {
  setIsShow(!isShow);
  console.log(isShow);
}
return (
  <div>
    <button onClick={() => toggle()}>trigger</button>
    <span style={{display: isShow ? 'static' : 'none'}}>content area</span>
  </div>);
 }
export default App;

```

But,when i add key in the span, it can work. Why?

```
<span key={isShow} style={{display: isShow ? 'static' : 'none'}}>content area</span>

```