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react/snippets/use-window-size.md

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+---
+title: React useWindowSize hook
+type: snippet
+tags: [hooks,state,effect]
+author: chalarangelo
+cover: polar-bear
+dateModified: 2021-10-18T05:00:00-04:00
+---
+
+Tracks the dimensions of the browser window.
+
+- Use the `useState()` hook to initialize a state variable that will hold the window's dimensions. Initialize with both values set to `undefined` to avoid mismatch between server and client renders.
+- Create a function that uses `Window.innerWidth` and `Window.innerHeight` to update the state variable.
+- Use the `useEffect()` hook to set an appropriate listener for the `'resize'` event on mount and clean it up when unmounting.
+
+```jsx
+const useWindowSize = () => {
+  const [windowSize, setWindowSize] = React.useState({
+    width: undefined,
+    height: undefined,
+  });
+
+  React.useEffect(() => {
+    const handleResize = () =>
+      setWindowSize({ width: window.innerWidth, height: window.innerHeight });
+
+    window.addEventListener('resize', handleResize);
+
+    handleResize();
+
+    return () => {
+      window.removeEventListener('resize', handleResize);
+    };
+  }, []);
+
+  return windowSize;
+};
+```
+
+```jsx
+const MyApp = () => {
+  const { width, height } = useWindowSize();
+
+  return (
+    <p>
+      Window size: ({width} x {height})
+    </p>
+  );
+};
+
+ReactDOM.createRoot(document.getElementById('root')).render(
+  <MyApp />
+);
+```