跟踪 React 组件重新渲染的原因 [英] Trace why a React component is re-rendering

问题描述

是否有系统的方法来调试导致组件在 React 中重新渲染的原因?我放了一个简单的 console.log() 来查看它渲染了多少次，但是我无法弄清楚是什么导致组件多次渲染，即在我的情况下(4 次).是否存在显示时间线和/或所有组件树渲染和顺序的工具?

Is there a systematic approach to debug what is causing a component to re-render in React? I put a simple console.log() to see how many time it renders, but am having trouble figuring out what is causing the component to render multiple times i.e (4 times) in my case. Is there a tool that exists that shows a timeline and/or all components tree renders and order?

推荐答案

如果你想要一个没有任何外部依赖的简短片段，我觉得这很有用

If you want a short snippet without any external dependencies I find this useful

componentDidUpdate(prevProps, prevState) {
  Object.entries(this.props).forEach(([key, val]) =>
    prevProps[key] !== val && console.log(`Prop '${key}' changed`)
  );
  if (this.state) {
    Object.entries(this.state).forEach(([key, val]) =>
      prevState[key] !== val && console.log(`State '${key}' changed`)
    );
  }
}

这是我用来跟踪功能组件更新的一个小钩子

Here is a small hook I use to trace updates to function components

function useTraceUpdate(props) {
  const prev = useRef(props);
  useEffect(() => {
    const changedProps = Object.entries(props).reduce((ps, [k, v]) => {
      if (prev.current[k] !== v) {
        ps[k] = [prev.current[k], v];
      }
      return ps;
    }, {});
    if (Object.keys(changedProps).length > 0) {
      console.log('Changed props:', changedProps);
    }
    prev.current = props;
  });
}

// Usage
function MyComponent(props) {
  useTraceUpdate(props);
  return <div>{props.children}</div>;
}

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