将 Hook 调用语句放置在代码的顶层，避免被包在条件语句中。

示例代码：

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

  // 错误的写法：在条件语句中调用了 Hook
  if (props.condition) {
    const [name, setName] = useState('John');
  }

  return (
    

      
You clicked { count } times.
       setCount(count + 1)}>
        Click me
      
    
  );
}

修改后的代码：

function MyComponent(props) {
  const [count, setCount] = useState(0);
  const [name, setName] = useState('John');

  // 正确的写法：将 Hook 放置在顶层
  if (props.condition) {
    // 修改 state 值
    setName('Lucy');
  }

  return (
    

      
You clicked { count } times.
      
Hello, { name }
       setCount(count + 1)}>
        Click me
      
    
  );
}