Intermediate code explainers

ruby

class DocumentsController < ApplicationController
  before_action :authenticate_user!
  before_action :set_document

Serving secure file downloads in Rails

authorization signed-urls active-storage

Intermediate 8 steps

go

package deepcopy
 
import (
	"bytes"

Deep copying any value with gob in Go

deep-copy serialization generics

Intermediate 6 steps

python

from decimal import Decimal, ROUND_HALF_UP
 
from babel.numbers import format_currency
from flask import Flask

Building a currency Jinja filter in Flask

template filters decimal precision internationalization

Intermediate 6 steps

rust

use axum::{
    body::Body,
    extract::MatchedPath,
    http::{Request, StatusCode},

An admin route guard in Axum middleware

middleware authorization request-extensions

Intermediate 7 steps

php

public function transaction(callable $callback, int $maxAttempts = 3): mixed
{
    $attempt = 0;

Retrying database deadlocks in PHP

retry transactions deadlock

Intermediate 8 steps

typescript

import {
  WebSocketGateway,
  WebSocketServer,
  SubscribeMessage,

Building a real-time chat gateway in NestJS

websockets real-time socket.io

Intermediate 8 steps

ruby

require "bigdecimal"
 
module Money
  CENTS = BigDecimal("0.01")

Handling money safely with BigDecimal in Ruby

bigdecimal rounding currency

Intermediate 7 steps

go

package handlers
 
import (
	"net/http"

Query-string filtering in Gin with GORM

query-binding validation conditional-queries

Intermediate 8 steps

javascript

import { useState, useRef, useEffect, useCallback } from 'react';
 
export function CopyButton({ text, label = 'Copy' }) {
  const [copied, setCopied] = useState(false);

A copy-to-clipboard button in React

clipboard-api hooks cleanup

Intermediate 7 steps

python

from functools import wraps
 
import jwt
from flask import current_app, g, jsonify, request

How a JWT auth decorator works in Flask

decorators authentication jwt

Intermediate 6 steps

javascript

const UNITS = ['B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB'];
 
export function formatBytes(bytes, { decimals = 1, binary = false } = {}) {
  if (!Number.isFinite(bytes)) {

Formatting byte counts into human units

logarithms formatting default-parameters

Intermediate 8 steps

rust

use std::collections::VecDeque;
 
pub struct RollingAverage {
    window: VecDeque<f64>,

A rolling average over a sliding window

sliding-window running-sum ring-buffer

Intermediate 6 steps

typescript

type CsvRecord = Record<string, string>;
 
function parseCsv(input: string): CsvRecord[] {
  const rows: string[][] = [];

Parsing CSV with a character state machine

state-machine parsing string-processing

Intermediate 8 steps

javascript

'use client';
 
import { useState, useTransition, useRef, useEffect, useCallback } from 'react';
import { loadMorePosts } from '@/app/actions/posts';

Infinite scroll with Server Actions in Next.js

infinite-scroll intersection-observer server-actions

Intermediate 8 steps

rust

use std::time::Duration;
 
#[derive(Debug, Clone)]
pub struct ServerConfig {

The builder pattern in Rust

builder-pattern ownership error-handling

Intermediate 8 steps

typescript

const ISO_DURATION = /^P(?:(\d+(?:\.\d+)?)Y)?(?:(\d+(?:\.\d+)?)M)?(?:(\d+(?:\.\d+)?)W)?(?:(\d+(?:\.\d+)?)D)?(?:T(?:(\d+(?:\.\d+)?)H)?(?:(\d+(?:\.\d+)?)M)?(?:(\d+(?:\.\d+)?)S)?)?$/;
 
const SECONDS_PER = {
  years: 365 * 24 * 60 * 60,

Parsing ISO 8601 durations to seconds

regex parsing iso-8601

Intermediate 7 steps

javascript

import { createContext, useContext, useEffect, useState, useCallback } from 'react';
 
const ThemeContext = createContext(null);

Building a theme provider with React Context

context hooks dark-mode

Intermediate 9 steps

rust

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum State {
    Locked,
    Unlocked,

A turnstile state machine in Rust

state machine enums pattern matching

Intermediate 9 steps