Jegyzet

Lomanu4 · 18 Май 2025

Vizsga-Jegyzet

Ami várhatóan közös minden feladatban:

Start

Az index.js-ben állítsd be a db portot port: 3307 ha kell

mkdir vizsga
cd vizsga
mkdir forras
mkdir asztali
mkdir backend
cd backend
npm i express mysql2 cors
npm pkg set type=module
echo import express from 'express'; > index.js
echo import cors from 'cors'; >> index.js
echo import mysql from 'mysql2'; >> index.js
echo. >> index.js
echo const app = express(); >> index.js
echo app.use(cors()); >> index.js
echo app.use(express.json()); >> index.js
echo. >> index.js
echo const db = mysql.createConnection(^{ >> index.js
echo host: 'localhost', >> index.js
echo user: 'root', >> index.js
echo password: '', >> index.js
echo database: 'adatbazis_nev', >> index.js
echo port: 3306 // esetenkent 3307 >> index.js
echo }); >> index.js
echo. >> index.js
echo // vegpontok >> index.js
echo. >> index.js
echo // Create / Post >> index.js
echo app.post('/', (req, res) =^> ^{ >> index.js
echo const { value1, value2} = req.body; >> index.js
echo db.query( >> index.js
echo 'INSERT INTO tabla_nev (value1, value2) VALUES ( ?, ?)', >> index.js
echo [value1, value2], >> index.js
echo (err, result) =^> ^{ >> index.js
echo if (err) { >> index.js
echo console.error('Create error:', err); >> index.js
echo return res.status(500).json({ message: 'Create error.' }); >> index.js
echo } >> index.js
echo res.json({ value1, value2}); >> index.js
echo } >> index.js
echo ); >> index.js
echo }); >> index.js
echo. >> index.js
echo // Read / Get >> index.js
echo app.get('/', (req, res) =^> ^{ >> index.js
echo db.query('SELECT * FROM tabla_nev', (err, results) =^> ^{ >> index.js
echo if (err) { >> index.js
echo console.error('Read error:', err); >> index.js
echo return res.status(500).json({ message: 'Read error.' }); >> index.js
echo } >> index.js
echo res.json(results); >> index.js
echo }); >> index.js
echo }); >> index.js
echo. >> index.js
echo // Update / Put >> index.js
echo app.put('/:id', (req, res) =^> ^{ >> index.js
echo const { value1, value2} = req.body; >> index.js
echo db.query( >> index.js
echo 'UPDATE tabla_nev SET value1 = ?, value2 = ? WHERE id = ?', >> index.js
echo [value1, value2, req.params.id], >> index.js
echo (err, result) =^> ^{ >> index.js
echo if (err) { >> index.js
echo console.error('Update error:', err); >> index.js
echo return res.status(500).json({ message: 'Update error.' }); >> index.js
echo } >> index.js
echo res.sendStatus(204); >> index.js
echo } >> index.js
echo ); >> index.js
echo }); >> index.js
echo. >> index.js
echo // Delete >> index.js
echo app.delete('/:id', (req, res) =^> ^{ >> index.js
echo db.query('DELETE FROM tabla_nev WHERE id = ?', [req.params.id], (err, result) =^> ^{ >> index.js
echo if (err) { >> index.js
echo console.error('Delete error:', err); >> index.js
echo return res.status(500).json({ message: 'Delete error.' }); >> index.js
echo } >> index.js
echo res.sendStatus(204); >> index.js
echo }); >> index.js
echo }); >> index.js
echo. >> index.js
echo app.listen(3000, () =^> ^{ >> index.js
echo console.log('Server is running on http://localhost:3000'); >> index.js
echo }); >> index.js

cd ..
npm create vite@latest frontend -- --template react
y
cd frontend
npm install
npm pkg set type=module
npm install axios react-router-dom
npm install react-bootstrap bootstrap bootstrap-icons
exit

Mindkét package.json-ban állítsd be "type": "module"

src/main.jsx Ha bootstrap nelkul hasznalod

import React from 'react'
import ReactDOM from 'react-dom/client'
import { BrowserRouter } from 'react-router-dom'
import App from './App'

ReactDOM.createRoot(document.getElementById('root')).render(
<React.StrictMode>
<BrowserRouter>
<App />
</BrowserRouter>
</React.StrictMode>,
)

src/App.jsx Ha bootstrap nelkul hasznalod

import React from 'react'
import { Routes, Route, Link } from 'react-router-dom'
import Home from './pages/Home'
import About from './pages/About'

export default function App() {
return (
<div>
<nav style={{ display: 'flex', gap: '1rem' }}>
<Link to="/">Főoldal</Link>
<Link to="/about">Rólunk</Link>
</nav>
<Routes>
<Route path="/" element={<Home />} />
<Route path="/about" element={<About />} />
</Routes>
</div>
)
}

[Ajanlott]
src/pages/Home.jsx

import React, { useEffect, useState } from 'react'
import axios from 'axios'

export default function Home() {
const [data, setData] = useState(null)

useEffect(() => {
axios.get('

Пожалуйста Авторизируйтесь или Зарегистрируйтесь для просмотра скрытого текста.

')
.then(response => setData(response.data))
.catch(error => console.error('Hiba történt:', error))
}, [])

return (
<div>
<h1>Főoldal</h1>
{data ? (
<div>
<h2>{data.title}</h2>
<p>{data.body}</p>
</div>
) : (
<p>Betöltés...</p>
)}
</div>
)
}

[Ajanlott]
src/pages/About.jsx

import React from 'react'

export default function About() {
return (
<div>
<h1>Rólunk</h1>
<p>Ez egy példa React alkalmazás a Vite használatával.</p>
</div>
)
}

[Ajanlott]
App.jsx a menü Bootstrap-el

import { BrowserRouter } from 'react-router-dom'
import 'bootstrap/dist/css/bootstrap.min.css'
import 'bootstrap/dist/js/bootstrap.bundle.min'
import 'bootstrap-icons/font/bootstrap-icons.css'
import { Routes, Route, Link } from 'react-router-dom'
import Home from './pages/Home'
import About from './pages/About'

export default function App() {
return (
<BrowserRouter>

<div>
<nav className="navbar navbar-expand-lg navbar-light bg-light">
<div className="container-fluid">
<Link className="navbar-brand" to="/">Weboldalam</Link>
<button
className="navbar-toggler"
type="button"
data-bs-toggle="collapse"
data-bs-target="#navbarNav"
aria-controls="navbarNav"
aria-expanded="false"
aria-label="Toggle navigation"
>
<span className="navbar-toggler-icon"></span>
</button>
<div className="collapse navbar-collapse" id="navbarNav">
<ul className="navbar-nav">
<li className="nav-item">
<Link className="nav-link" to="/">Főoldal</Link>
</li>
<li className="nav-item">
<Link className="nav-link" to="/about">Rólunk</Link>
</li>
</ul>
</div>
</div>
</nav>

<div className="container mt-4">
<Routes>
<Route path="/" element={<Home />} />
<Route path="/about" element={<About />} />
</Routes>
</div>
</div>
</BrowserRouter>
)
}

[!WARNING]

A App.css illetve az index.css tartalmat torolni kell a Bootstrap miatt.

DESKTOP Console

using System.IO;

struct listaElemek
{
public string hegycsucsNeve;
public string hegyseg;
public string magassag;
}

static void Main(string[] args)
{
listaElemek hegy = new listaElemek();
List<listaElemek> hegyek = new List<listaElemek>();

FileStream folyam = new FileStream("hegyekMo.txt", FileMode.Open);
StreamReader olvas = new StreamReader(folyam);

string elso = olvas.ReadLine();
string[] resz;

while (!olvas.EndOfStream)
{
elso = olvas.ReadLine();

resz = elso.Split(';');
hegy.hegycsucsNeve = resz[0];
hegy.hegyseg = resz[1];
hegy.magassag = resz[2];
hegyek.Add(hegy);
}

double seged = 0;
for (int i = 0; i < hegyek.Count; i++)
{
seged += Convert.ToInt32(hegyek.magassag);
}

double legnagyobb = 0;
int seged2 = 0;
for (int i = 0; i < hegyek.Count; i++)
{
if (legnagyobb < Convert.ToInt32(hegyek.magassag))
{
legnagyobb = Convert.ToInt32(hegyek.magassag); seged2 = i;
}
}

Console.WriteLine($"3. feladat: Hegycsúcsok száma: {hegyek.Count} db");
Console.WriteLine($"4. feladat: Hegycsúcsok átlagos magassága: {seged / hegyek.Count} m");
Console.WriteLine($"5. feladat: Legmagasabb hegycsúcs adatai: " +
$"\n\tNév: {hegyek[seged2].hegycsucsNeve}" +
$"\n\tHegység: {hegyek[seged2].hegyseg}" +
$"\n\tMagassága: {hegyek[seged2].magassag} m");
Console.Write($"6. feladat: Kérek egy magasságot: ");
string bekertAdat = Console.ReadLine();

string seged3 = "Van";
for (int i = 0; i < hegyek.Count; i++)
{
if ((hegyek.hegyseg == "Börzsöny") && (Convert.ToInt32(hegyek.magassag) < Convert.ToInt32(bekertAdat)))
{
seged3 = "Nincs";
}
}

Console.WriteLine($"\t{seged3} {bekertAdat}m-nél magasabb hegycsúcs a Börzsönyben!");

double seged4 = 3.280839895;
int megfeleloHegyekSzama = 0;
for (int i = 0; i < hegyek.Count; i++)
{
if ((Convert.ToInt32(hegyek.magassag) * seged4) > 3000)
{
megfeleloHegyekSzama++;
}
}
Console.WriteLine($"7. feladat: 3000 lábnál magasabb hegycsúcsok száma: {megfeleloHegyekSzama}");

string[] seged5 = {"Mátra", "Bükk-vidék", "Börzsöny", "Zempléni-hegység", "Kőszegi-hegység" };
int matra = 0, bukk = 0, borzsony = 0, zemplen = 0, koszeg = 0;

for (int i = 0; i < hegyek.Count; i++)
{
for (int j = 0; j < seged5.Length; j++)
{
if (hegyek.hegyseg.Contains(seged5[j]))
{
if (seged5[j] == "Mátra")
{
matra++;
}
if (seged5[j] == "Bükk-vidék")
{
bukk++;
}
if (seged5[j] == "Börzsöny")
{
borzsony++;
}
if (seged5[j] == "Zempléni-hegység")
{
zemplen++;
}
if (seged5[j] == "Kőszegi-hegység")
{
koszeg++;
}
}
}
}

Console.WriteLine($"8. feladat: Hegység statisztika" +
$"\n\t{seged5[0]} - {matra} db" +
$"\n\t{seged5[1]} - {bukk} db" +
$"\n\t{seged5[2]} - {borzsony} db" +
$"\n\t{seged5[3]} - {zemplen} db" +
$"\n\t{seged5[4]} - {koszeg} db");

Console.WriteLine("9. feladat: bukk-videk.txt");

string path = "bukk-videk.txt";
if (!File.Exists(path))
{
File.Create(path);
TextWriter tw = new StreamWriter(path);
tw.WriteLine("Hegycsúcs neve;Magasság láb");
tw.Close();
}
else if (File.Exists(path))
{
TextWriter tw = new StreamWriter(path);
for (int i = 0; i < hegyek.Count; i++)
{
if (hegyek.hegyseg == "Bükk-vidék")
{
tw.WriteLine($"{hegyek.hegycsucsNeve};{Convert.ToInt32(hegyek.magassag) * seged4}");
}
}
tw.Close();
}
Console.ReadKey();
}
howToSolve Console

General Guide

Useful Webpages

Пожалуйста Авторизируйтесь или Зарегистрируйтесь для просмотра скрытого текста.

Пожалуйста Авторизируйтесь или Зарегистрируйтесь для просмотра скрытого текста.

Пожалуйста Авторизируйтесь или Зарегистрируйтесь для просмотра скрытого текста.

VSC Extensions:

EasyZoom

Live Server

Thunder Client

Auto Rename Tag

If XAMPP Won't Start

Navigate to: C:\xampp\mysql\backup

Press Ctrl + X to cut the contents

Navigate to: C:\xampp\mysql\data

Press Ctrl + A to select all, then Ctrl + P to paste

Desktop

Target finish time: ~1h 25min

Text manipulation

Replace(',','-'); // 2019-2-12
Trim('-'); // 2019212
Split(','); // {apple, banana, orange}
Contains("YES") // returns true

char[] nameArray = {'A', 'l', 'i', 'c', 'e'};
string name = new string(nameArray);

Math.Round(number, 2)); // 5.43529 -> 5.44 (Honorable mention: Floor(), Ceiling())
Classes and Constructors

class Person
{
public int id { get; set; }
public double average { get; set; }
public string name { get; set; }
public DateTime date { get; set; }

public Person(int id, double average, string name, DateTime date)
{
this.id = id;
this.average = average;
this.name = name;
this.date = date;
}
}
Reading a File

List<Person> peopleList = new List<Person>();

using (StreamReader sr = new StreamReader("filename.txt"))
{
while (!sr.EndOfStream)
{
string line = sr.ReadLine();
string[] data = line.Split(';');
int id = int.Parse(data[0]);
data[1] = data[1].Replace(',', '.');
double atlag = double.Parse(data[1]);
string name = data[2];
DateTime date = Convert.ToDateTime(data[3]);
Person personList = new Person(id, average, name, date);
peopleList.Add(person);
}
}
Creating a File

using (StreamWriter sw = File.CreateText("filename.txt"))
{
sw.WriteLine("...");
}
LINQ Examples

using System.Linq;
1. Aggregation (Count, Sum, Average, Max, Min)

Calculate statistics.

int count = people.Count(); // Total people
int over30Count = people.Count(p => p.Age > 30); // People over 30
double totalSalary = people.Sum(p => p.Salary); // Total salary
double avgSalary = people.Average(p => p.Salary); // Average salary
int maxAge = people.Max(p => p.Age); // Oldest age
2. Filtering (Where)

Select people older than 25.

var olderThan25 = people.Where(p => p.Age > 25);
3. Sorting (OrderBy, ThenBy)

Sort people by age, then by name.

var sortedPeople = people.OrderBy(p => p.Age).ThenBy(p => p.Name);
4. Selecting Specific Fields (Select)

Get a list of names and salaries.

var namesAndSalaries = people.Select(p => new { p.Name, p.Salary });
5. Grouping (GroupBy)

Group people by age.

var groupedByAge = people.GroupBy(p => p.Age).Select(g => new { Age = g.Key, People = g });
6. First, Last, Single

Get specific elements.

Person firstPerson = people.First(); // First person
Person lastPerson = people.Last(); // Last person
Person singlePerson = people.Single(p => p.Id == 1); // Person with Id 1
7. Any and All

Check conditions.

bool hasYoung = people.Any(p => p.Age < 25); // True if any person is under 25
bool allHighEarners = people.All(p => p.Salary > 40000); // True if all earn > 40k
Tips for Effective LINQ

Performance: Avoid multiple enumerations; materialize results with .ToList() if needed.

Debugging: Break complex queries into smaller steps.

Backend

Target finish time: ~1h

Endpoints

import express from "express";
import mysql from "mysql2";
import cors from "cors";

const app = express();
const port = 3000;

app.use(express.json());
app.use(cors());

const db = mysql.createConnection({
host: "localhost",
user: "root",
password: "",
database: "namedays",
});

// API endpoint to get nameday by date
app.get("/api/nameday/", (req, res) => {
// Extract "date" from query parameter
const date = req.query.date; // KEY

// Check if date is specified
if (!date) {
return res.status(400).json({ error: "Date parameter is required" });
}

// get the month and day
const month = date.split("-")[0];
const monthName = convertMonthNumberToName(month);
const day = date.split("-")[1];
const sql = SELECT name1, name2 FROM nameday WHERE month = ${month} AND day = ${day};

db.query(sql, (err, result) => {
if (err) {
console.log("Server error");
}
if (result.length === 0) {
console.log("No nameday found");
}
const nameday = result[0];

// Send response with formatted date and nameday data
res.json({ // KEY
date: `${monthName} ${day}.`,
name1: nameday.name1,
name2: nameday.name2,
});
});
});

// Function to convert month number to month name
function convertMonthNumberToName(monthNumber) {
switch (monthNumber) {
case "1":
return "January";
case "2":
return "February";
...
}
}

// Delete data by ID
app.delete("/api/nameday/:id", async (req, res)=>{
const id = req.params.id; // Extracts the ID from the URL parameter, e.g., /api/nameday/123
const sql = "DELETE FROM nameday WHERE id = ?";
const [result] = await database.execute(sql, [id]);
res.status(200).json(result);
})

app.listen(port, () => {
console.log(`Server is running on port ${port}`);
});
Frontend

Target finish time: ~1h 30min

Import Bootstrap

<link href="

Пожалуйста Авторизируйтесь или Зарегистрируйтесь для просмотра скрытого текста.

" rel="stylesheet" integrity="sha384-4Q6Gf2aSP4eDXB8Miphtr37CMZZQ5oXLH2yaXMJ2w8e2ZtHTl7GptT4jmndRuHDT" crossorigin="anonymous">
Display and submit cards dynamically using Bootstrap

<div class="container"> 
<form id="dateForm" class="mb-4">
<div class="row g-3 align-items-end">
<div class="col-auto">
<label for="dateInput" class="form-label">Select Date:</label>
<input type="date" id="dateInput" class="form-control" required>
</div>
<div class="col-auto">
<button type="submit" class="btn btn-primary">Get Nameday</button>
</div>
</div>
</form>
</div>

<div id="namedayCards" class="row row-cols-1 row-cols-md-2 g-4"></div> // Place for the cards

<script>
// Handle form submission
document.getElementById('dateForm').addEventListener('submit', async (e) => {
e.preventDefault();
const date = document.getElementById('dateInput').value;
if (!date) return;

// Clear previous cards
const cardContainer = document.getElementById('namedayCards');
cardContainer.innerHTML = '';

// Fetch data from API
try {
const response = await fetch(`

Пожалуйста Авторизируйтесь или Зарегистрируйтесь для просмотра скрытого текста.

{date}`);
if (!response.ok) {
throw new Error('Failed to fetch nameday data');
}
const data = await response.json();

// Check for error response
if (data.error) {
cardContainer.innerHTML = `<div class="alert alert-warning">${data.error}</div>`;
return;
}

// Create Bootstrap cards for each name
const names = [data.name1, data.name2];
names.forEach(name => {
const card = document.createElement('div');
card.className = 'col';
card.innerHTML = `
<div class="card h-100">
<div class="card-body">
<h5 class="card-title">${name}</h5>
<p class="card-text">Nameday on ${data.date}</p>
</div>
</div>
`;
cardContainer.appendChild(card);
});
} catch (error) {
console.error('Error:', error);
cardContainer.innerHTML = `<div class="alert alert-danger">Error fetching data</div>`;
}
});
</script>
WinForms

ember.cs Class

public int id { get; set; }
public string nev { get; set; }
public int kor { get; set; }

public Ember(int id, string nev, int kor)
{
this.id = id;
this.nev = nev;
this.kor = kor;
}

program.cs

public Form1()
{
InitializeComponent();
}
int id = 0; // Globális változó az ID-hez
private void Form1_Load(object sender, EventArgs e)
{

}
private void button1_Click(object sender, EventArgs e)
{
OpenFileDialog openFileDialog = new OpenFileDialog();

// Beállítások (opcionális)
openFileDialog.InitialDirectory = "C:\\";
openFileDialog.Filter = "CSV fájlok (*.csv)|*.csv|Minden fájl (*.*)|*.*";
openFileDialog.FilterIndex = 1;
openFileDialog.RestoreDirectory = true;

// Ha a felhasználó kiválasztott egy fájlt
if (openFileDialog.ShowDialog() == DialogResult.OK)
{
// Fájl elérési útja
string filePath = openFileDialog.FileName;

// Például: kiírjuk egy Label-re vagy feldolgozzuk
MessageBox.Show("Kiválasztott fájl: " + filePath);

List<Ember> emberek = new List<Ember>();

FileStream folyam = new FileStream(filePath, FileMode.Open);
StreamReader olvas = new StreamReader(folyam);

string elso = olvas.ReadLine();
string[] resz;

while (!olvas.EndOfStream)
{
elso = olvas.ReadLine();

resz = elso.Split(';');
Ember personList = new Ember(int.Parse(resz[0]), resz[1], int.Parse(resz[2]));
emberek.Add(personList);
id++;
}
olvas.Close();
folyam.Close();

// A lista feltöltése
for (int i = 0; i < emberek.Count; i++)
{
// listBox
listBox1.Items.Add(emberek.id + ", " + emberek.nev + ", " + emberek.kor);
}
}
}

private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
{
if (listBox1.SelectedItem != null)
{
// Kiválasztott sor szövege
string selectedLine = listBox1.SelectedItem.ToString();

// Sor feldarabolása pontosvessző mentén
string[] parts = selectedLine.Split(',');

if (parts.Length == 3)
{
textBox_id.Text = parts[0];
textBox_nev.Text = parts[1];
textBox_kor.Text = parts[2];
}
}
}

private void button_Create_Click(object sender, EventArgs e)
{
id++;
listBox1.Items.Add(id + ", " + textBox_nev.Text + ", " + textBox_kor.Text);

}

private void button_Update_Click(object sender, EventArgs e)
{
string updatedLine = $"{textBox_id.Text}, {textBox_nev.Text}, {textBox_kor.Text}";

// Kijelölt elem cseréje az új értékre
int selectedIndex = listBox1.SelectedIndex;
listBox1.Items[selectedIndex] = updatedLine;
}

private void button_Delete_Click(object sender, EventArgs e)
{
listBox1.Items.Remove(listBox1.SelectedItem);
}

export to bin/Debug

private void button_export_Click(object sender, EventArgs e)
{
string fileName = "exportalt_adatok.csv";
string exportPath = Path.Combine(Application.StartupPath, fileName);

using (StreamWriter writer = new StreamWriter(exportPath, false, Encoding.UTF8))
{
// Fejléc (ha kell)
writer.WriteLine("id;nev;kor");

foreach (var item in listBox1.Items)
{
string line = item.ToString(); // "id, nev, kor"
string[] parts = line.Split(','); // [id, nev, kor]

// Trim miatt: szóközök eltávolítása
string formattedLine = $"{parts[0].Trim()};{parts[1].Trim()};{parts[2].Trim()}";
writer.WriteLine(formattedLine);
}
MessageBox.Show("Exportálás kész: " + exportPath);
writer.Close();
}
}

export to kivalasztott hely

private void button_export_Click(object sender, EventArgs e)
{
SaveFileDialog saveFileDialog = new SaveFileDialog();
saveFileDialog.Filter = "CSV fájlok (*.csv)|*.csv";
saveFileDialog.Title = "Mentés CSV fájlba";
saveFileDialog.FileName = "kimentett_adatok.csv";

if (saveFileDialog.ShowDialog() == DialogResult.OK)
{
try
{
using (StreamWriter writer = new StreamWriter(saveFileDialog.FileName, false, Encoding.UTF8))
{
// Fejléc (ha kell)
writer.WriteLine("id;nev;kor");

foreach (var item in listBox1.Items)
{
string line = item.ToString(); // "id, nev, kor"
string[] parts = line.Split(','); // [id, nev, kor]

// Trim miatt: szóközök eltávolítása
string formattedLine = $"{parts[0].Trim()};{parts[1].Trim()};{parts[2].Trim()}";
writer.WriteLine(formattedLine);
}
}

MessageBox.Show("Sikeres exportálás!");
}
catch (Exception ex)
{
MessageBox.Show("Hiba történt: " + ex.Message);
}
}
}

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Jegyzet

Lomanu4