Intermediate code explainers

javascript

import { unstable_cache, revalidateTag } from 'next/cache'
import { db } from '@/lib/db'
 
export const getDashboardStats = unstable_cache(

Caching dashboard stats in Next.js

caching cache-invalidation tag-based-revalidation

Intermediate 8 steps

java

@Component
@Order(Ordered.HIGHEST_PRECEDENCE)
public class TenantResolutionFilter extends OncePerRequestFilter {

How a tenant-resolution filter works in Spring

multi-tenancy servlet-filter thread-local

Intermediate 8 steps

rust

pub fn format_size(bytes: u64) -> String {
    const UNITS: [&str; 7] = ["B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB"];
 
    if bytes < 1024 {

Formatting byte counts as human-readable sizes

bit-manipulation formatting unit-conversion

Intermediate 5 steps

python

import click
from flask.cli import AppGroup
 
from . import db

Custom user CLI commands in Flask

cli click command-group

Intermediate 7 steps

typescript

interface ParsedName {
  first: string;
  middle: string;
  last: string;

Parsing human names into structured parts

parsing string-manipulation normalization

Intermediate 9 steps

go

package middleware
 
import (
	"compress/gzip"

How gzip HTTP middleware works in Go

middleware compression object-pooling

Intermediate 7 steps

ruby

require 'set'
 
class DirectoryWatcher
  def initialize(path, pattern: '**/*', interval: 1.0)

Polling for file changes in Ruby

polling filesystem diffing

Intermediate 7 steps

php

<?php
 
namespace App\Experiments;

Weighted random selection in PHP

weighted-random cumulative-sum sampling

Intermediate 8 steps

javascript

import { Component } from 'react';
import { reportError } from './services/telemetry';
 
export class ErrorBoundary extends Component {

How a React ErrorBoundary works

error-handling lifecycle-methods render-props

Intermediate 8 steps

java

@Repository
public interface SubscriptionRepository extends JpaRepository<Subscription, Long> {
 
    @Modifying(clearAutomatically = true, flushAutomatically = true)

Bulk JPQL updates in a Spring Data repository

jpql bulk-update modifying-query

Intermediate 5 steps

python

import heapq
from datetime import datetime
from pathlib import Path
from typing import Iterator, NamedTuple

Merging sorted log files with heapq

generators heapq lazy-evaluation

Intermediate 6 steps

typescript

import { useCallback, useEffect, useRef, useState } from "react";
 
interface UseResendCooldownOptions {
  cooldownSeconds?: number;

A resend cooldown hook in React

custom-hooks timers state-management

Intermediate 7 steps

go

package events
 
import (
	"net/http"

Two-pass JSON dispatch in Gin

polymorphic-json request-binding validation

Intermediate 8 steps

ruby

class HashDiff
  Change = Struct.new(:from, :to)
 
  def self.call(before, after)

Diffing two hashes in Ruby

set-operations struct enumerable

Intermediate 7 steps

php

final class FieldEncryptor
{
    private string $key;

Authenticated field encryption with libsodium

encryption libsodium authenticated-encryption

Intermediate 7 steps

javascript

const FOCUSABLE = [
  'a[href]',
  'button:not([disabled])',
  'input:not([disabled])',

How to trap keyboard focus in a dialog

accessibility dom event-handling

Intermediate 8 steps

java

package com.example.uploads.config;
 
import jakarta.servlet.MultipartConfigElement;
import org.springframework.boot.web.servlet.MultipartConfigFactory;

Configuring upload size limits in Spring

file-upload exception-handling http-errors

Intermediate 6 steps

python

import datetime
from dataclasses import dataclass

Parsing fixed-width records in Python

parsing generators dataclasses

Intermediate 8 steps