useEffect6.js

import React, { useState, useEffect } from "react";

const MyComponent = () => {
  const [width, setWidth] = useState(window.innerWidth);
  
  useEffect(() => {
    const handleResize = () => setWidth(window.innerWidth);
    window.addEventListener("resize", handleResize);
    
    return () => {
      window.removeEventListener("resize", handleResize);
    }
  }, []);

  render() {
    return (
      <h1>{this.state.width}</h1>
    );
  }
}