Intermediate code explainers

javascript

'use client';
 
import { useActionState } from 'react';
import { submitSignup } from './actions';

Multi-step forms with useActionState in Next.js

server-actions form-state progressive-enhancement

Intermediate 10 steps

rust

use axum::{
    body::Body,
    extract::Request,
    http::{header, StatusCode},

A CSRF verification middleware in Axum

csrf middleware security

Intermediate 10 steps

typescript

import { useCallback, useId, useRef, useState, type KeyboardEvent } from 'react';
 
interface Tab {
  id: string;

Building an accessible tabs component in React

accessibility aria keyboard-navigation

Intermediate 8 steps

java

public final class MapFlattener {
 
    private MapFlattener() {
    }

Flattening nested maps into dotted keys

recursion tree-traversal data-transformation

Intermediate 7 steps

php

<?php
 
namespace App\Http\Controllers;

Conditional query building in Laravel

query-builder conditional-logic closures

Intermediate 7 steps

javascript

import { notFound } from 'next/navigation'
import { getPhotoById } from '@/lib/photos'
import Modal from '@/components/modal'
import Image from 'next/image'

An intercepted photo modal route in Next.js

dynamic-routes async-components metadata

Intermediate 6 steps

ruby

def wrap_text(text, width = 80)
  raise ArgumentError, "width must be positive" unless width.positive?
 
  text.split(/\n/, -1).map do |paragraph|

How greedy text wrapping works in Ruby

string-processing greedy-algorithm text-wrapping

Intermediate 7 steps

rust

pub fn extract_quoted_fields(line: &str) -> Vec<String> {
    let mut fields = Vec::new();
    let mut current = String::new();
    let mut in_quotes = false;

Parsing quoted fields with a state machine in Rust

state-machine parsing string-processing

Intermediate 7 steps

python

from flask import Flask, request, redirect, current_app
from werkzeug.middleware.proxy_fix import ProxyFix
 
app = Flask(__name__)

Enforcing HTTPS behind a proxy in Flask

https middleware security-headers

Intermediate 7 steps

java

package com.example.actuator;
 
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.actuate.endpoint.annotation.Endpoint;

Building a custom Spring Boot Actuator endpoint

actuator dependency-injection observability

Intermediate 7 steps

php

<?php
 
namespace App\Notifications;

Delayed, self-cancelling emails in Laravel

queues notifications delayed-jobs

Intermediate 7 steps

ruby

class SyncInventoryJob < ApplicationJob
  queue_as :integrations
 
  retry_on Faraday::TimeoutError,

Resilient background jobs with retry_on in Rails

background-jobs error-handling retries

Intermediate 8 steps

python

import fnmatch
from collections import defaultdict
from typing import Any, Callable

A pattern-matching event bus in Python

pub-sub decorators pattern-matching

Intermediate 8 steps

ruby

class Pluralizer
  IRREGULARS = {
    "person" => "people",
    "child" => "children",

Building an English pluralizer in Ruby

regular-expressions lookup-tables string-manipulation

Intermediate 8 steps

javascript

import type { MetadataRoute } from 'next'
 
const BASE_URL = process.env.NEXT_PUBLIC_SITE_URL ?? 'https://example.com'

Environment-aware robots.txt in Next.js

seo environment-config web-crawlers

Intermediate 6 steps

php

<?php
 
namespace App\Support;

Detecting file types by MIME in PHP

file-validation mime-detection whitelist

Intermediate 7 steps

python

from typing import Iterable
 
 
def jaccard_similarity(tags_a: Iterable[str], tags_b: Iterable[str]) -> float:

Ranking tag sets by Jaccard similarity

set-operations similarity-metric generators

Intermediate 5 steps

java

@Configuration
public class ValidationConfig implements WebMvcConfigurer {
 
    @Bean

Localized bean validation messages in Spring

internationalization bean-validation configuration

Intermediate 6 steps