Intermediate code explainers

typescript

interface ContentRange {
  unit: string;
  start: number;
  end: number;

Parsing HTTP Content-Range headers in TypeScript

regex parsing validation

Intermediate 8 steps

rust

use axum::{
    async_trait,
    extract::FromRequestParts,
    http::{header::HeaderValue, request::Parts, HeaderName},

Propagating trace context in Axum extractors

extractors distributed-tracing http-headers

Intermediate 8 steps

ruby

require 'set'
 
class CronSchedule
  FIELDS = %i[minute hour day month wday].freeze

Parsing and matching cron expressions in Ruby

parsing time-arithmetic sets

Intermediate 10 steps

javascript

const fs = require('fs');
const path = require('path');
const express = require('express');

Streaming video with HTTP range requests in Express

http-range-requests streaming path-traversal

Intermediate 8 steps

php

<?php
 
namespace App\Http\Controllers;

Serving cached translations from a Laravel controller

http-caching etag localization

Intermediate 8 steps

python

from django import forms
from django.contrib.auth import get_user_model
from django.shortcuts import redirect
from formtools.wizard.views import SessionWizardView

Building a multi-step form with Django wizards

form-wizard multi-step-forms session-state

Intermediate 8 steps

go

package flatten
 
import (
	"encoding/json"

Flattening nested JSON into dotted keys

recursion json type-switch

Intermediate 7 steps

typescript

type CacheEntry<V> = {
  value: V;
  computedAt: number;
};

A TTL cache keyed by object identity

caching weakmap generics

Intermediate 8 steps

rust

use std::fs::File;
use std::io::{self, BufRead, BufReader};
use std::path::Path;

Streaming lines from a gzip file in Rust

iterators io-streaming decompression

Intermediate 6 steps

ruby

module MarkdownHelper
  ALLOWED_TAGS = %w[
    p br strong em del a ul ol li blockquote code pre
    h1 h2 h3 h4 h5 h6 hr img table thead tbody tr th td

Safely rendering Markdown in a Rails helper

sanitization markdown security

Intermediate 8 steps

php

<?php
 
namespace App\Services;

Validating coupons before applying a discount in Laravel

validation guard clauses business rules

Intermediate 7 steps

python

import functools
import time
 
from flask import current_app

Retrying deadlocked DB writes in Flask

decorators retry exponential-backoff

Intermediate 6 steps

go

func HandleWebhook(store WebhookStore, dispatcher *EventDispatcher) gin.HandlerFunc {
	return func(c *gin.Context) {
		body, err := c.GetRawData()
		if err != nil {

Building a resilient webhook handler in Gin

webhooks dependency-injection signature-verification

Intermediate 9 steps

ruby

class ActivityFeed
  include Enumerable
 
  Entry = Struct.new(:record, :type, :occurred_at, keyword_init: true) do

Building a paginated activity feed in Rails

enumerable pagination composition

Intermediate 9 steps

python

import time
import logging
from threading import Lock

Rate-limiting noisy logs in Python

throttling thread-safety logging

Intermediate 6 steps

php

<?php
 
namespace App\Services\Analytics;

Building a signup chart with Laravel's query builder

aggregation date-ranges query-builder

Intermediate 6 steps

typescript

import { Injectable, Scope } from '@nestjs/common';
import DataLoader from 'dataloader';
import { InjectRepository } from '@nestjs/typeorm';
import { In, Repository } from 'typeorm';

Batching queries with DataLoader in NestJS

dataloader batching n+1

Intermediate 7 steps

javascript

const { z, ZodError } = require('zod');
 
function validate(schemas) {
  return (req, res, next) => {

A reusable Zod validation middleware for Express

middleware validation schema

Intermediate 8 steps