Intermediate code explainers

rust

use std::net::Ipv4Addr;
use std::str::FromStr;
 
#[derive(Debug, Clone, Copy)]

Parsing and matching IPv4 CIDR ranges in Rust

bitwise-operations parsing error-handling

Intermediate 8 steps

typescript

type CsvColumn<T> = {
  header: string;
  value: (row: T) => string | number | boolean | null | undefined;
};

Building a type-safe CSV writer in TypeScript

generics serialization escaping

Intermediate 7 steps

java

@RestController
@RequestMapping("/api/products")
public class ProductSearchController {

Binding collection query params in Spring

rest-api query-parameters dependency-injection

Intermediate 6 steps

ruby

class Api::MessagesController < ApiController
  before_action :authenticate_api_key!
 
  rate_limit to: 100,

Layered API rate limiting in Rails

rate-limiting api-authentication throttling

Intermediate 9 steps

php

<?php
 
namespace App\Http\Middleware;

Resolving the current team in Laravel middleware

middleware multi-tenancy cookies

Intermediate 8 steps

go

package scheduler
 
import (
	"container/heap"

A priority job queue with Go's container/heap

priority-queue heap interfaces

Intermediate 9 steps

python

import os
from pathlib import Path
 
BASE_DIR = Path(__file__).resolve().parent.parent.parent

How a Django settings module is wired

configuration environment-variables middleware

Intermediate 8 steps

rust

use std::sync::OnceLock;
 
static CRC_TABLE: OnceLock<[u32; 256]> = OnceLock::new();

Table-driven CRC32 with lazy init in Rust

checksums lazy-initialization lookup-tables

Intermediate 8 steps

typescript

import { parsePhoneNumberFromString, CountryCode } from 'libphonenumber-js';
 
export interface NormalizedPhone {
  e164: string;

Normalizing phone numbers to E.164 in TypeScript

validation normalization error-handling

Intermediate 7 steps

java

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Map;

Evaluating math expressions with two stacks

stacks parsing operator-precedence

Intermediate 9 steps

ruby

class Order < ApplicationRecord
  include AASM
 
  belongs_to :warehouse

Modeling an order lifecycle with AASM in Rails

state machine guards callbacks

Intermediate 10 steps

php

<?php
 
namespace App\Http\Controllers;

Broadcasting typing indicators in Laravel

websockets authorization presence-channels

Intermediate 9 steps

ruby

require "timeout"
require "net/http"
 
class RemoteInventoryClient

Bounding a slow HTTP call with Timeout in Ruby

timeout error-handling http

Intermediate 6 steps

java

@Entity
@Table(name = "orders")
@SQLDelete(sql = "UPDATE orders SET deleted = true, deleted_at = now() WHERE id = ?")
@Where(clause = "deleted = false")

Soft deletes with Hibernate in Spring

soft-delete jpa hibernate

Intermediate 9 steps

javascript

import { useState, useEffect, useCallback } from 'react';
 
function getColumnCount(width) {
  if (width < 640) return 1;

A responsive column hook in React

custom-hooks debouncing responsive-design

Intermediate 7 steps

php

<?php
 
namespace App\Services\Reports;

Streaming a monthly revenue CSV in Laravel

csv-export lazy-collections eloquent-query

Intermediate 8 steps

python

def is_valid_card_number(number: str) -> bool:
    digits = [int(c) for c in number if c.isdigit()]
 
    if len(digits) < 13 or len(digits) > 19:

Validating card numbers with the Luhn check

checksum validation luhn-algorithm

Intermediate 6 steps

go

func (h *ArticleHandler) Create(c *gin.Context) {
	var req struct {
		Title   string `json:"title" binding:"required"`
		Body    string `json:"body" binding:"required"`

Handling a POST request in Gin

request binding validation http status codes

Intermediate 7 steps