Intermediate code explainers

ruby

require "phonelib"
 
class PhoneNumber
  class InvalidNumber < StandardError; end

Wrapping phone parsing in a Ruby value object

value-object memoization validation

Intermediate 7 steps

java

package com.example.config.condition;
 
import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;

A custom @Conditional feature flag in Spring

conditional beans feature flags annotations

Intermediate 7 steps

go

package middleware
 
import (
	"errors"

Capping request body size in Gin

middleware request limits error handling

Intermediate 5 steps

typescript

import { Component } from '@angular/core';
import { NgForm } from '@angular/forms';
 
interface SignupModel {

How template-driven forms validate in Angular

forms two-way-binding validation

Intermediate 9 steps

rust

#[derive(Debug, PartialEq)]
enum State {
    FieldStart,
    InUnquoted,

Parsing a CSV line with a state machine

state machine parsing enums

Intermediate 9 steps

ruby

class PaymentGateway
  class MissingCredentialError < StandardError; end
 
  def initialize(env: Rails.env)

Wrapping Rails credentials in a gateway

encapsulation credentials error handling

Intermediate 6 steps

java

public List<OrderSummary> streamRecentOrders(LocalDateTime since, Consumer<OrderSummary> handler) {
    String sql = """
        SELECT id, customer_id, total_cents, status, created_at
        FROM orders

Streaming large JDBC result sets safely

jdbc streaming resource-management

Intermediate 7 steps

javascript

import { useState, useEffect, useCallback } from 'react';
 
export function useCountdown(initialSeconds) {
  const [secondsLeft, setSecondsLeft] = useState(initialSeconds);

Building a useCountdown hook in React

custom-hooks state-management side-effects

Intermediate 8 steps

go

package batch
 
import "fmt"

Splitting a slice into batches in Go

generics slices error-handling

Intermediate 6 steps

typescript

import { Injectable, signal, computed } from '@angular/core';
 
export type ToastKind = 'success' | 'error' | 'info' | 'warning';

Building a signal-based toast service in Angular

signals state-management dependency-injection

Intermediate 8 steps

python

from flask import Blueprint, request, jsonify
from marshmallow import Schema, fields, validate, ValidationError, EXCLUDE
 
from .models import db, User

How a Flask blueprint validates and creates users

validation rest-api schema

Intermediate 8 steps

php

<?php
 
namespace App\Console\Commands;

How a database backup command works in Laravel

artisan-command shell-process error-handling

Intermediate 8 steps

ruby

class WelcomeSequenceOrchestrator
  STEPS = [
    { mailer: :welcome_email,      delay: 0.hours },
    { mailer: :getting_started,    delay: 1.day },

Scheduling a drip email sequence in Rails

mailers background jobs scheduling

Intermediate 6 steps

typescript

import { Controller } from '@nestjs/common';
import {
  MessagePattern,
  Payload,

Manual RabbitMQ acks in a NestJS controller

microservices message-queue acknowledgement

Intermediate 8 steps

rust

use std::convert::TryFrom;
 
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum HttpStatus {

Converting HTTP codes with TryFrom in Rust

enums error-handling trait-implementation

Intermediate 8 steps

python

import random
 
import click
from faker import Faker

Building a Flask seed command with Click

cli database seeding orm

Intermediate 7 steps

typescript

type LazyImageOptions = {
  rootMargin?: string;
  loadedClass?: string;
};

Lazy-loading images with IntersectionObserver

intersectionobserver lazy-loading performance

Intermediate 7 steps

rust

use axum::{
    extract::{Request, State},
    http::{HeaderValue, StatusCode},
    middleware::Next,

API version headers with Axum middleware

middleware http-headers versioning

Intermediate 8 steps