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in Technique[技术] by (71.8m points)

react hook 初始化问题

大佬们问一下
问题一: 为什么这个run会打印两次

const App: React.FC = () => {
  console.log("run");
  const [count, setCount] = useState(0);
  return (
    <div>
      <p>{count}</p>
      <button onClick={() => setCount(count)}>click</button>
    </div>
  );
};
export default App;

问题二:
为什么第一点击结果是[1,1] 第二次[1,1,1,1],
第三次[1,1,1,1,1,1] 除了第一次点击加1,后面每次加2个1

const App: React.FC = () => {
  console.log("run");
  const [count, setCount] = useState([1]);
  const push = () => {
    setCount((count) => {
      count.push(1)
      return [...count]
    })
  }
  return (
    <div>
      <p>{JSON.stringify(count)}</p>
      <button onClick={push}>click</button>
    </div>
  );
};
export default App;

这个两个问题应该是有联系吧感觉


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
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1 Answer

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by (71.8m points)

第一个问题,只有开发环境下会执行两次,打包后会正常执行


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
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