First modal example App.js

modal-1.js

import { useState } from "react";
import "./App.css";

function App() {
  const [isOpen, setOpen] = useState(false);

  return (
    <div className="container">
      <button onClick={() => setOpen(true)} className="open-btn">
        Open Modal
      </button>
      <div
        onClick={() => setOpen(false)}
        className={`underlay ${isOpen ? "open" : ""}`}
      />
      <div className={`modal ${isOpen ? "open" : ""}`}></div>
    </div>
  );
}

export default App;