react useeffect

import React, { useState, useEffect } from 'react';
function Example() {
  const [count, setCount] = useState(0);

  useEffect(() => {    document.title = `You clicked ${count} times`;  });
  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>
        Click me
      </button>
    </div>
  );
}

import React, { useState, useEffect } from 'react';
function Example() {
  const [count, setCount] = useState(0);

  // Similar to componentDidMount and componentDidUpdate:  
  useEffect(() => {    
  	// Update the document title using the browser API    
  	document.title = `You clicked ${count} times`;  
  });
  
  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>
        Click me
      </button>
    </div>
  );
}

import {useEffect, useState} from 'react';

export default function App() {
  const [counter, setCounter] = useState(0);


  // ✅ hook is called at top level (not conditionally)
  useEffect(() => {
    if (counter > 0) {
      console.log('hello world');
    }
  });

  return (
    <div>
      <button onClick={() => setCounter(counter + 1)}>toggle loading</button>
      <h1>Hello world</h1>
    </div>
  );
}

import { useState, useEffect } from 'react';

function App() {

  const [pieceOfState, setPieceOfState] = useState(0);

  useEffect(() => {
    console.log('I\'m in useEffect!');
    console.log('This will be called whenever an instance of this component mounts');
    console.log('or whenever pieceOfState is updated');
  }, [pieceOfState]);

  return (
    <div>
      <button onClick={() => setPieceOfState(pieceOfState + 1)}>Click Me to Update pieceOfState!</button>
    </div>
  );
}