Intermediate code explainers

typescript

import {
  CallHandler,
  ExecutionContext,
  Injectable,

Wrapping responses in a NestJS interceptor

interceptors rxjs response-shaping

Intermediate 7 steps

rust

use std::collections::HashMap;
use std::sync::{Arc, Mutex};
use std::thread;

Aggregating metrics across threads in Rust

concurrency shared-state mutex

Intermediate 7 steps

python

import argparse
import sys
from pathlib import Path

Building a subcommand CLI with argparse

cli argparse subcommands

Intermediate 6 steps

go

package main
 
import (
	"errors"

Parsing and validating CLI flags in Go

cli-parsing validation error-handling

Intermediate 8 steps

ruby

require "csv"
 
class SalesReport
  def initialize(path)

Aggregating CSV sales data in Ruby

data-aggregation memoization group_by

Intermediate 6 steps

javascript

'use server'
 
import { revalidatePath } from 'next/cache'
import { redirect } from 'next/navigation'

How a Next.js Server Action updates a post

server-actions authorization validation

Intermediate 7 steps

java

public class ThumbnailProcessor {
 
    private static final int MAX_CONCURRENCY = 4;

Bounded parallel thumbnail rendering in Java

concurrency thread-pool futures

Intermediate 7 steps

php

<?php
 
namespace App\Support;

Locale-aware formatting with PHP's intl extension

internationalization encapsulation constructor-injection

Intermediate 7 steps

typescript

type RetryOptions = {
  retries?: number;
  timeoutMs?: number;
  baseDelayMs?: number;

Retry with timeout and backoff in TypeScript

promises retry exponential-backoff

Intermediate 10 steps

python

from collections.abc import Mapping
from typing import Any, Iterator

Flattening nested config into dotted keys

recursion generators tree-traversal

Intermediate 7 steps

ruby

module DurationFormatter
  UNITS = [
    ['week', 604_800],
    ['day', 86_400],

Turning seconds into human-readable durations in Ruby

greedy-decomposition modular-arithmetic formatting

Intermediate 7 steps

javascript

const express = require('express');
 
const v1 = express.Router();

Versioning an API with Express Routers

api versioning routing modularity

Intermediate 10 steps

php

<?php
 
namespace App\Support;

Merging query params onto a URL in PHP

url-parsing query-strings immutability

Intermediate 8 steps

python

import csv
import io
from datetime import datetime

Streaming a CSV export in Flask

streaming generators csv

Intermediate 9 steps

go

package cache
 
import (
	"container/list"

Building a generic LRU cache in Go

lru-cache generics linked-list

Intermediate 8 steps

php

<?php
 
class ImageUploadService
{

Validating file uploads safely in PHP

file-upload input-validation security

Intermediate 8 steps

ruby

class Comment < ApplicationRecord
  belongs_to :post
  belongs_to :author, class_name: "User"

Live-updating comments with Turbo in Rails

turbo-streams callbacks associations

Intermediate 8 steps

python

import time
from collections import defaultdict
from threading import Lock

Sliding-window login rate limiting in Flask

rate-limiting sliding-window thread-safety

Intermediate 7 steps