Can jQuery and React coexist on the same page?

Yes, they can coexist.

jQuery and React solve different tasks and can be used in parallel on the same page. React manages components and interface state, while jQuery can be used for DOM manipulations outside React's control or for working with third-party plugins that depend on jQuery.

It is important to be cautious to avoid direct manipulations of DOM elements managed by React using jQuery. This can disrupt React's internal state and lead to unpredictable behavior.

Recommended approach:

1. React manages the main rendering and UI state.
2. jQuery is used for:
   • Third-party widgets and plugins requiring jQuery.
   • DOM manipulations in areas of the page not under React's control.
   • Simple AJAX requests or utilities if there's no need to switch to fetch or other libraries.

Example of using jQuery inside a React component (with caution):

import React, { useEffect, useRef } from 'react';
import $ from 'jquery'; // Import jQuery

function MyComponent() {
  const elementRef = useRef(null);

  useEffect(() => {
    // Direct DOM manipulation only inside useEffect
    // Ensure this element is not directly managed by React via state/props
    if (elementRef.current) {
      $(elementRef.current).css('color', 'blue'); // Example of using jQuery
    }

    // Cleanup effect on component unmount
    return () => {
      // Cleanup if jQuery applied any listeners or changes
    };
  }, []); // Empty dependency array, effect runs only once on mount

  return (
    <div ref={elementRef}>
      This text will be blue.
    </div>
  );
}

export default MyComponent;

Using :after and :before in CSS modules:

Yes, pseudo-elements :after and :before can be used in CSS modules. The syntax is standard.

/* MyComponent.module.css */
.container::before {
  content: "Start ";
  color: green;
}

.container::after {
  content: " End";
  color: red;
}

/* Usage in React component */
import styles from './MyComponent.module.css';

function MyComponent() {
  return (
    <div className={styles.container}>
      Main text
    </div>
  );
}

Pseudo-elements :after and :before are part of CSS syntax and do not depend on how styles are loaded or modularized in React. They are processed by the browser after styles are applied.