how to useref in class component code example

Example 1: useRef

/*
	A common use case is to access a child imperatively: 
*/

function TextInputWithFocusButton() {
  const inputEl = useRef(null);
  const onButtonClick = () => {
    // `current` points to the mounted text input element
    inputEl.current.focus();
  };
  return (
    <>
      <input ref={inputEl} type="text" />
      <button onClick={onButtonClick}>Focus the input</button>
    </>
  );
}

Example 2: useref react

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

export default function (props) {
  // Initialized a hook to hold the reference to the title div.
  const titleRef = useRef();
  
  useEffect(function () {
    setTimeout(() => {
      titleRef.current.textContent = "Updated Text"
    }, 2000); // Update the content of the element after 2seconds 
  }, []);
  
  return <div className="container">
    {/** The reference to the element happens here **/ }
    <div className="title" ref={titleRef}>Original title</div>
  </div>
}