How to make connections without this error?

[Lomanu4]

General Guide

Create Project Directory inside terminal


mkdir "Project name"
cd "Project name"

mkdir backend
mkdir "subdirectory2"
mkdir "subdirectory3"
Useful Webpages

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VSC Extensions:

• EasyZoom
• Live Server
• Thunder Client
• Auto Rename Tag

If XAMPP Won't Start

1. Navigate to: C:\xampp\mysql\backup
2. Press Ctrl + X to cut the contents
3. Navigate to: C:\xampp\mysql\data
4. Press Ctrl + A to select all, then Ctrl + P to paste

Desktop


Target finish time: ~1h 25min

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;
}
}
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())
Reading a File


using System.IO;

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 person = 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;

foreach (var group in groupedByYear)
{
Console.WriteLine($"Year: {group.Year}");
foreach (var person in group.People)
{
Console.WriteLine($"- {person.Name}");
}
}
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

Setup Node.js Express

Installs necessary packages inside backend folder and creates app.js/index.js file with basic content


cd backend
npm install express mysql2 cors
npm pkg set type=module
cd backend
echo "import express from 'express';" > app.js
echo "import cors from 'cors';" >> app.js
echo "import mysql from 'mysql2';" >> app.js
echo "" >> app.js
echo "const app = express();" >> app.js
echo "app.use(cors());" >> app.js
echo "app.use(express.json());" >> app.js
echo "" >> app.js
echo "const db = mysql.createConnection({" >> app.js
echo " host: 'localhost'," >> app.js
echo " user: 'root'," >> app.js
echo " password: ''," >> app.js
echo " database: '', // Database name goes here" >> app.js
echo " port: 3306" >> app.js
echo "});" >> app.js
echo "" >> app.js
echo "// endpoints" >> app.js
echo "" >> app.js
echo "app.listen(3000, () => {" >> app.js
echo " console.log('Server is running on http://localhost:3000');" >> app.js
echo "});" >> app.js
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="

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


<div class="container"> <!-- To make the page responsive -->
<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(`

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{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>

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