Handy But Hazy Programming Tasks: Java, Python, JavaScript

handy-snippets.txt

## 🔁 String & Text Manipulation

### Slugify a string

**JavaScript**
```js
function slugify(str) {
  return str.toLowerCase().replace(/\s+/g, '-').replace(/[^a-z0-9-]/g, '');
}
```

**Python**
```py
import re

def slugify(text):
    return re.sub(r'[^a-z0-9-]', '', re.sub(r'\s+', '-', text.lower()))
```

**Java**
```java
public static String slugify(String input) {
    return input.toLowerCase().replaceAll("\\s+", "-").replaceAll("[^a-z0-9-]", "");
}
```

---

### Escape/Unescape HTML

**JavaScript**
```js
function escapeHTML(str) {
  return str.replace(/[&<>"']/g, c => ({'&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#39;'}[c]));
}
```

**Python**
```py
import html
html.escape("<div>")  # '&lt;div&gt;'
html.unescape("&lt;div&gt;")  # '<div>'
```

**Java**
```java
import org.apache.commons.text.StringEscapeUtils;
StringEscapeUtils.escapeHtml4("<div>");
StringEscapeUtils.unescapeHtml4("&lt;div&gt;");
```

---

## 📁 File Operations

### Read all files in a directory (non-recursive)

**JavaScript (Node.js)**
```js
const fs = require('fs');
fs.readdirSync('./path').forEach(file => console.log(file));
```

**Python**
```py
import os
for f in os.listdir('./path'):
    print(f)
```

**Java**
```java
import java.io.File;
File folder = new File("./path");
for (File file : folder.listFiles()) {
    System.out.println(file.getName());
}
```

---

## 🧮 Date & Time

### Get current timestamp

**JavaScript**
```js
Date.now();
```

**Python**
```py
import time
time.time()
```

**Java**
```java
System.currentTimeMillis();
```

---

### Add 5 days to current date

**JavaScript**
```js
let d = new Date();
d.setDate(d.getDate() + 5);
```

**Python**
```py
from datetime import datetime, timedelta
print(datetime.now() + timedelta(days=5))
```

**Java**
```java
import java.time.LocalDate;
LocalDate.now().plusDays(5);
```

---

## 🧵 Async/Concurrency

### Sleep for 1 second

**JavaScript**
```js
await new Promise(res => setTimeout(res, 1000));
```

**Python**
```py
import time
time.sleep(1)
```

**Java**
```java
Thread.sleep(1000);  // in milliseconds
```

---

## 🔐 Security & Hashing

### Hash a string (SHA-256)

**JavaScript (Node.js)**
```js
const crypto = require('crypto');
crypto.createHash('sha256').update('hello').digest('hex');
```

**Python**
```py
import hashlib
hashlib.sha256(b'hello').hexdigest()
```

**Java**
```java
import java.security.MessageDigest;
MessageDigest md = MessageDigest.getInstance("SHA-256");
byte[] hash = md.digest("hello".getBytes(StandardCharsets.UTF_8));
String hex = DatatypeConverter.printHexBinary(hash);
```

---

## 🌐 Network

### Simple HTTP GET

**JavaScript (fetch)**
```js
fetch('https://example.com').then(res => res.text()).then(console.log);
```

**Python**
```py
import requests
response = requests.get('https://example.com')
print(response.text)
```

**Java**
```java
import java.net.*;
import java.io.*;
URL url = new URL("https://example.com");
BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
String inputLine;
while ((inputLine = in.readLine()) != null)
    System.out.println(inputLine);
in.close();
```