Use of ref

import { useRef } from "react";

const myRef = useRef(null);

import { useRef } from "react";

function App() {
  const inputRef = useRef(null);

  return (
    <>
      
       inputRef.current.focus()}>
        Focus Input
      
    
  );
}

import { useRef, useState } from "react";

function App() {
  const renderCount = useRef(0);
  const [count, setCount] = useState(0);

  renderCount.current++;

  return (
    <>
      
Count: {count}
      
Renders: {renderCount.current}
       setCount(count + 1)}>+
    
  );
}

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

function App() {
  const [count, setCount] = useState(0);
  const prevCount = useRef(null);

  useEffect(() => {
    prevCount.current = count;
  }, [count]);

  return (
    <>
      
Current: {count}
      
Previous: {prevCount.current}
       setCount(count + 1)}>+
    
  );
}

import { useRef, useState } from "react";

function Stopwatch() {
  const timerRef = useRef(null);
  const [time, setTime] = useState(0);

  const start = () => {
    if (!timerRef.current) {
      timerRef.current = setInterval(() => {
        setTime(t => t + 1);
      }, 1000);
    }
  };

  const stop = () => {
    clearInterval(timerRef.current);
    timerRef.current = null;
  };

  return (
    <>
      
Time: {time}s
      Start
      Stop
    
  );
}