最近正在看React

有看到兩個例子，想請教一下

function ExampleA() {
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>
        Click me
      </button>
    </div>
  );
}

function ExampleB() {
  const [obj, setObject] = useState({
  
    count: 0,
    name: "ml"
  });
  return (
    <div>
      Count: {obj.count}
      <button onClick={() => setObject({ ...obj, count: obj.count + 1 })}>+</button>
    </div>
  );
}

1.為什麼ExampleB的Hook要這樣寫?還有他的setObject也為什麼要這樣寫?
我看這兩個執行結果都差不多，不太清楚他們的差異

2.Example的setCount裡他是這樣寫

<button onClick={() => setCount(count + 1)}>

但我看到有網站說這樣比較安全

<button onClick={() => setCount(prevCount => prevCount + 1)}>

https://medium.com/@xyz030206/%E9%97%9C%E6%96%BC-usestate-%E4%BD%A0%E9%9C%80%E8%A6%81%E7%9F%A5%E9%81%93%E7%9A%84%E4%BA%8B-5c8c4cdda82c

真的是如他所說的嗎?我看滿多範例都還是單純的(count+1)

這些我暫時還不太懂，所以想請問一下