Code Explainers

Browse the library

go 
package fetch
 
import (
	"context"

Concurrent API fetches with errgroup in Go

concurrency goroutines error-handling
Intermediate 8 steps
javascript 
export function cloneState(state) {
  if (typeof structuredClone !== "function") {
    throw new Error("structuredClone is not available in this runtime");
  }

Deep cloning with structuredClone

deep-copy error-handling immutability
Intermediate 7 steps
rust 
use serde::Deserialize;
use serde_json::Value;
use std::collections::HashMap;
 

Modeling nested JSON with serde in Rust

deserialization json struct-mapping
Intermediate 9 steps
java 
import java.util.concurrent.atomic.AtomicInteger;
 
public final class RequestCounter {
 

A thread-safe request counter with AtomicInteger

concurrency atomics lock-free
Intermediate 6 steps
typescript 
import { inject } from '@angular/core';
import {
  CanActivateFn,
  Router,

Functional route guards in Angular

route-guards dependency-injection observables
Intermediate 5 steps
python 
import threading
import logging
 
logger = logging.getLogger(__name__)

A self-rescheduling periodic task in Python

threading scheduling concurrency
Intermediate 6 steps
go 
func UploadFiles(c *gin.Context) {
	form, err := c.MultipartForm()
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid multipart form"})

Handling multi-file uploads in Gin

file-upload multipart validation
Intermediate 8 steps
php 
<?php
 
namespace App\Services;
 

Caching tenant dashboard metrics in Laravel

caching multi-tenancy aggregation
Intermediate 7 steps
rust 
use axum::{
    body::Bytes,
    extract::State,
    http::{HeaderMap, StatusCode},

Verifying Stripe webhook signatures in Axum

hmac webhooks constant-time-comparison
Intermediate 8 steps
go 
package pipeline
 
import (
	"context"

A cancelable worker pool in Go

concurrency channels worker-pool
Advanced 8 steps
python 
from collections import ChainMap
from functools import reduce
from typing import Any, Iterable, Mapping
 

Five ways to merge dicts in Python

dictionaries merging recursion
Intermediate 8 steps
java 
@Service
public class ReportGenerationService {
 
    private final ReportRepository reportRepository;

Async report generation with Spring @Async

async dependency-injection completablefuture
Intermediate 7 steps
ruby 
class PurgeStaleExportsJob < ApplicationJob
  queue_as :maintenance
 
  retry_on ActiveRecord::Deadlocked, wait: :polynomially_longer, attempts: 5

Purging stale exports with an Active Job in Rails

background-jobs batching error-handling
Intermediate 7 steps
php 
<?php
 
namespace App\Http\Controllers\Auth;
 

Rate-limited login in Laravel

authentication rate-limiting validation
Intermediate 9 steps
typescript 
import {
  CanActivate,
  ExecutionContext,
  Injectable,

Role-based route guards in NestJS

authorization decorators metadata-reflection
Intermediate 8 steps
rust 
use axum::{
    body::Body,
    extract::Request,
    http::{header, StatusCode},

How bearer-auth middleware works in Axum

middleware authentication request extensions
Intermediate 7 steps
javascript 
function validateSignup({ email, password, confirmPassword, username, age }) {
  const errors = {};
 
  if (!email) {

Building a signup validator in JavaScript

validation regex guard-clauses
Beginner 7 steps
go 
package auth
 
import (
	"net/http"

Building a JWT auth middleware in Gin

middleware jwt authentication
Intermediate 7 steps