Intermediate code explainers

javascript

const RESERVED_SLUGS = new Set(['new', 'edit', 'admin', 'api']);
 
function slugify(title) {
  return title

Generating URL-safe unique slugs

string-normalization regex deduplication

Intermediate 9 steps

go

package api
 
func RegisterRoutes(r *gin.Engine, deps *Dependencies) {
	r.GET("/health", func(c *gin.Context) {

Layering route groups and middleware in Gin

routing middleware authentication

Intermediate 8 steps

ruby

class Product < ApplicationRecord
  belongs_to :account
 
  after_save :record_audit_trail

Building an audit trail with Rails callbacks

callbacks audit-logging dirty-tracking

Intermediate 7 steps

php

<?php
 
function buildTree(array $items, ?int $parentId = null): array
{

Building a tree from a flat list in PHP

recursion tree grouping

Intermediate 6 steps

python

from datetime import datetime, date
from decimal import Decimal
from flask import Flask, jsonify
from flask.json.provider import DefaultJSONProvider

Serializing SQLAlchemy models in Flask JSON

serialization orm json

Intermediate 6 steps

java

@Component
@Order(20)
public class ProductSearchIndexRunner implements ApplicationRunner {

Rebuilding a search index at Spring startup

startup-hook batching streaming

Intermediate 8 steps

typescript

export class PriorityQueue<T> {
  private heap: Array<{ value: T; priority: number }> = [];
 
  get size(): number {

Building a binary-heap priority queue in TypeScript

binary-heap priority-queue generics

Intermediate 9 steps

javascript

class EventEmitter {
  constructor() {
    this.listeners = new Map();
  }

Building an EventEmitter in JavaScript

pub-sub closures map

Intermediate 7 steps

go

package payments
 
import (
	"context"

Fetching a charge over HTTP in Go

context-timeout http-client json-decoding

Intermediate 6 steps

ruby

class User < ApplicationRecord
  store_accessor :preferences,
    :theme,
    :timezone,

Storing user settings in a JSON column with Rails

store_accessor json-columns validations

Intermediate 7 steps

php

final class ConfigResolver
{
    private array $merged;

Layered config merging in PHP

recursion immutability variadics

Intermediate 8 steps

python

import requests
from requests.adapters import HTTPAdapter
from urllib3.util.retry import Retry

Building a resilient requests Session

retries backoff http-client

Intermediate 7 steps

java

public final class FileChecksum {
 
    private static final char[] HEX = "0123456789abcdef".toCharArray();

Streaming a SHA-256 file checksum in Java

hashing streams resource-management

Intermediate 7 steps

typescript

import { Injectable, signal, computed } from '@angular/core';
import {
  HttpInterceptorFn,
  HttpContextToken,

Tracking HTTP loading state in Angular

signals http-interceptor reference-counting

Intermediate 8 steps

javascript

const express = require('express');
const compression = require('compression');
const zlib = require('zlib');

Tuning Express response compression

compression middleware http

Intermediate 9 steps

go

package scheduler
 
import (
	"context"

A context-aware heartbeat ticker in Go

concurrency channels context

Intermediate 5 steps

ruby

require "time"
require "tzinfo"
 
module TimeConverter

Converting timestamps across time zones with TZInfo

timezones iso8601 parsing

Intermediate 8 steps

php

<?php
 
function uploadDocument(string $endpoint, string $filePath, array $meta): array
{

Uploading a file with cURL in PHP

curl file-upload http

Intermediate 8 steps