Intermediate code explainers

go

package api
 
import (
	"encoding/json"

Building reusable JSON helpers in Go HTTP handlers

http json error-handling

Intermediate 9 steps

java

package com.example.security;
 
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;

Salted password hashing with PBKDF2 in Java

password-hashing pbkdf2 salting

Intermediate 7 steps

typescript

interface PaginationParams {
  totalItems: number;
  pageSize: number;
  currentPage: number;

Building safe pagination metadata in TypeScript

pagination input-validation pure-functions

Intermediate 7 steps

ruby

require "forwardable"
 
class ShoppingCart
  extend Forwardable

Delegation in Ruby with Forwardable

delegation composition enumerable

Intermediate 9 steps

javascript

import { useRef, useState, useCallback, useMemo } from 'react';
 
export function VirtualList({ items, rowHeight = 40, height = 600, overscan = 5, renderRow }) {
  const [scrollTop, setScrollTop] = useState(0);

How a virtualized list works in React

virtualization performance memoization

Intermediate 8 steps

rust

use axum::{
    routing::get,
    Json, Router,
};

Response compression in Axum with tower-http

middleware compression http

Intermediate 6 steps

go

package server
 
import (
	"net/http"

Serving cached static assets in Gin

caching static-files middleware

Intermediate 7 steps

python

import re
import unicodedata
 
_SLUG_STRIP = re.compile(r"[^\w\s-]")

Building URL-safe slugs in Python

string-processing regex unicode-normalization

Intermediate 7 steps

java

package com.example.orders.repository;
 
import com.example.orders.domain.Order;
import org.springframework.data.jpa.repository.JpaRepository;

Projection interfaces in Spring Data JPA

projections jpql aggregation

Intermediate 7 steps

php

<?php
 
function parseMultipartEmail(string $raw): array
{

Parsing multipart emails with mailparse

mime-parsing email encoding

Intermediate 9 steps

ruby

class PaymentMethod < ApplicationRecord
  belongs_to :account
 
  encrypts :card_number, deterministic: false

How Rails encrypts sensitive payment fields

encryption validation scopes

Intermediate 9 steps

rust

use std::collections::HashMap;
 
#[derive(Debug, Clone)]
struct Row {

Building a tree from flat parent-id rows in Rust

recursion hashmap tree-building

Intermediate 6 steps

go

package middleware
 
import (
	"net/http"

Per-IP rate limiting middleware in Gin

rate-limiting token-bucket concurrency

Intermediate 7 steps

python

import os
import tarfile
from pathlib import Path

Safely compressing and extracting tar.gz archives

file-io compression path-traversal

Intermediate 6 steps

java

@RefreshScope
@Component
public class FeatureSettings {

Refreshable feature settings in Spring

caching configuration dependency-injection

Intermediate 7 steps

typescript

import { useEffect, useRef, useState } from "react";
 
export function useClickOutside<T extends HTMLElement>() {
  const ref = useRef<T>(null);

A dismiss-on-outside-click hook in React

custom-hooks event-listeners cleanup

Intermediate 7 steps

php

<?php
 
namespace App\Resilience;

How a circuit breaker guards a flaky service

circuit-breaker resilience caching

Intermediate 9 steps

ruby

require "zlib"
require "stringio"
require "base64"

Compress-and-encode payloads in Ruby

compression encoding io-streams

Intermediate 8 steps