React.js：使用 window 调整事件监听器的 useEffect 不起作用

Question

I'm using this code to listen for resize events in a function component and rerender the component when the window is resized. The problem is, nothing ever gets printed out for either event listener, so I think I have a misunderstanding of how I'm using useEffect here.

  const [dimensions, setDimensions] = React.useState({
    width: window.innerWidth,
    height: window.innerHeight,
  });

  useEffect(() => {
    const handleResize = () => {
      console.log(dimensions.width);
      setDimensions({
        width: window.innerWidth,
        height: window.innerHeight,
      });
      window.addEventListener("load", handleResize, false);
      window.addEventListener("resize", handleResize, false);
    };
  });

Answer 1

const [dimensions, setDimensions] = React.useState({
    width: window.innerWidth,
    height: window.innerHeight,
  });
  console.log(dimensions);
  const handleResize = () => {
    setDimensions({
      width: window.innerWidth,
      height: window.innerHeight,
    });
  }
  React.useEffect(() => {
    window.addEventListener("resize", handleResize, false);
  }, []);

  

Answer 2

import { useState, useEffect } from "react";
// Usage
function App() {
  const size = useWindowSize();
  return (
    <div>
      {size.width}px / {size.height}px
    </div>
  );
}
// Hook
function useWindowSize() {
  // Initialize state with undefined width/height so server and client renders match
  // Learn more here: https://joshwcomeau.com/react/the-perils-of-rehydration/
  const [windowSize, setWindowSize] = useState({
    width: undefined,
    height: undefined,
  });
  useEffect(() => {
    // Handler to call on window resize
    function handleResize() {
      // Set window width/height to state
      setWindowSize({
        width: window.innerWidth,
        height: window.innerHeight,
      });
    }
    // Add event listener
    window.addEventListener("resize", handleResize);
    // Call handler right away so state gets updated with initial window size
    handleResize();
    // Remove event listener on cleanup
    return () => window.removeEventListener("resize", handleResize);
  }, []); // Empty array ensures that effect is only run on mount
  return windowSize;
}

SOURCE

Answer 3

I found that the event listener on "resize" was not sufficient to populate the window dimensions in the initial load of the page. The following worked for me.

function getWindowDimensions() {
  const {innerWidth: width, innerHeight: height} = window;
  return {
    width,
    height
  };
}

function useWindowDimensions() {
  const defaultDim = {width: null, height: null}
  const [windowDimensions, setWindowDimensions] = useState(defaultDim);

  useEffect(() => {
    setWindowDimensions(getWindowDimensions()) // Necessary to make sure dimensions are set upon initial load

    function handleResize() {
      setWindowDimensions(getWindowDimensions());
    }

    window.addEventListener('resize', handleResize);
    return () => window.removeEventListener('resize', handleResize);
  }, []);

  return windowDimensions;
}