Intermediate code explainers

rust

use std::collections::HashMap;
 
#[derive(Clone, Copy, PartialEq)]
enum Color {

Detecting cycles with three-color DFS in Rust

graph-algorithms cycle-detection depth-first-search

Intermediate 9 steps

typescript

import { useCallback, useRef, useState } from "react";
 
type UploadZoneProps = {
  accept?: string[];

A drag-and-drop file upload zone in React

drag-and-drop file-validation controlled-state

Intermediate 9 steps

ruby

class MailingListDeduplicator
  GMAIL_DOMAINS = %w[gmail.com googlemail.com].freeze
 
  def initialize(subscribers)

Deduplicating a mailing list by canonical email

deduplication normalization service object

Intermediate 8 steps

go

package middleware
 
import (
	"fmt"

How a panic-recovery middleware works in Gin

middleware panic-recovery error-reporting

Intermediate 8 steps

java

public Map<Long, CustomerDto> indexByCustomerId(List<CustomerDto> customers) {
    return customers.stream()
            .collect(Collectors.toMap(
                    CustomerDto::getId,

Building maps from lists with Collectors.toMap

streams collectors maps

Intermediate 5 steps

python

from flask import Blueprint, render_template, redirect, url_for, session, request
from wtforms import Form, StringField, SelectField, IntegerField
from wtforms.validators import DataRequired, Email, NumberRange

A multi-step signup wizard in Flask

blueprints session-state form-validation

Intermediate 10 steps

javascript

class ToastQueue {
  constructor(container, { duration = 4000, max = 3 } = {}) {
    this.container = container;
    this.duration = duration;

Building a rate-limited toast queue

queue dom manipulation throttling

Intermediate 8 steps

rust

#[derive(Deserialize)]
pub struct CreateArticle {
    title: String,
    body: String,

Building a create endpoint in Axum

extractors json-deserialization sqlx

Intermediate 7 steps

java

@Service
public class InventoryService {
 
    private final RestClient warehouseClient;

Bulkhead-protected HTTP calls in Spring

bulkhead resilience fallback

Intermediate 7 steps

go

func UploadDocument(c *gin.Context) {
	fileHeader, err := c.FormFile("file")
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "file is required"})

Handling multipart uploads in Gin

multipart-upload validation error-handling

Intermediate 9 steps

php

<?php
 
namespace App\Models\Concerns;

Building soft deletes as an Eloquent trait in Laravel

traits soft-delete global-scope

Intermediate 10 steps

rust

use std::sync::Arc;
use std::sync::atomic::{AtomicBool, Ordering};
 
use axum::body::Body;

A maintenance-mode gate in Axum

middleware shared-state atomics

Intermediate 7 steps

python

from itertools import cycle
from collections import defaultdict

Round-robin task distribution in Python

round-robin iterators load-balancing

Intermediate 6 steps

javascript

import { useCallback, useState } from "react";
 
const MIN = 0;
const MAX = 1000;

Building a dual-thumb price slider in React

controlled-components state-clamping usecallback

Intermediate 8 steps

ruby

class ProgressBar
  BAR_WIDTH = 40
 
  def initialize(total, io: $stdout)

Building a terminal progress bar in Ruby

state tracking terminal output time estimation

Intermediate 8 steps

java

@Configuration
public class DataSourceLoggingConfig {
 
    @Bean

Wrapping a Spring DataSource for query tracing

proxy pattern observability data source

Intermediate 7 steps

go

package handlers
 
type WebhookEvent struct {
	ID   string          `json:"id"`

Verifying and processing webhooks in Gin

webhooks hmac idempotency

Intermediate 9 steps

php

<?php
 
namespace App\Services;

Idempotent role assignment in Laravel

many-to-many pivot-data idempotency

Intermediate 8 steps