Intermediate code explainers

go

func (h *WebhookHandler) HandleBatch(c *gin.Context) {
	var payload BatchWebhookPayload
	if err := c.ShouldBindJSON(&payload); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid payload"})

Handling batched webhooks in Gin

webhooks signature-verification job-queue

Intermediate 7 steps

ruby

require "net/http"
require "json"
require "uri"
require "base64"

Paginating an HTTP API with a Ruby enumerator

pagination http enumerator

Intermediate 7 steps

javascript

class StarRating {
  constructor(container, { max = 5, value = 0, onChange } = {}) {
    this.container = container;
    this.max = max;

Building an accessible star-rating widget

dom event-handling accessibility

Intermediate 7 steps

python

from pathlib import Path
from collections import defaultdict
 
from PIL import Image

Finding near-duplicate images by perceptual hash

perceptual-hashing clustering hamming-distance

Intermediate 9 steps

rust

use axum::{
    body::Body,
    http::{Method, StatusCode, Uri},
    response::{IntoResponse, Response},

Nesting routers and JSON fallbacks in Axum

routing http json-responses

Intermediate 7 steps

java

@Configuration
@EnableKafka
public class KafkaErrorHandlingConfig {

Kafka retry and dead-letter handling in Spring

kafka error-handling retry

Intermediate 7 steps

php

<?php
 
namespace App\Http\Controllers\Api;

Building a cursor-paginated feed in Laravel

cursor-pagination eager-loading validation

Intermediate 8 steps

typescript

import { useCallback, useEffect, useRef, useState } from "react";
 
interface Page<T> {
  items: T[];

A cursor-based infinite scroll hook in React

custom-hooks pagination intersection-observer

Intermediate 9 steps

go

package config
 
import "time"

The functional options pattern in Go

functional-options closures immutability

Intermediate 7 steps

ruby

class DateRangeMerger
  def initialize(ranges)
    @ranges = ranges
  end

Merging overlapping date ranges in Ruby

sorting interval-merging enumerable

Intermediate 5 steps

javascript

const form = document.querySelector('#signup-form');
const password = form.querySelector('#password');
const confirm = form.querySelector('#confirm-password');
const submit = form.querySelector('button[type="submit"]');

Live password-match validation in the DOM

form-validation dom-events accessibility

Intermediate 6 steps

rust

use axum::{
    extract::FromRequestParts,
    http::{request::Parts, StatusCode, header::ACCEPT_LANGUAGE},
};

A locale extractor for Axum handlers

content-negotiation http-headers custom-extractor

Intermediate 7 steps

java

@Controller
@RequestMapping("/employees")
public class EmployeeController {

Customizing form binding in a Spring MVC controller

data-binding validation type-conversion

Intermediate 9 steps

php

<?php
 
namespace App\Services;

Caching per-tenant settings in Laravel

caching multi-tenancy dependency-injection

Intermediate 7 steps

typescript

type NestedValue = string | NestedValue[] | { [key: string]: NestedValue };
 
function parseFieldPath(name: string): string[] {
  const match = name.match(/^([^\[\]]+)((?:\[[^\[\]]*\])*)$/);

Parsing bracketed form field names into nested objects

parsing recursive-types regex

Intermediate 8 steps

go

package admin
 
import (
	"net/http"

Building a protected admin area in Gin

routing middleware authentication

Intermediate 6 steps

ruby

module SlowQueryLogger
  SLOW_QUERY_THRESHOLD_MS = 200.0
  IGNORED_PAYLOAD_NAMES = %w[SCHEMA TRANSACTION].freeze

Logging slow SQL queries in Rails

instrumentation logging pub-sub

Intermediate 7 steps

python

import logging
import uuid
from contextvars import ContextVar

Request ID tracing in FastAPI middleware

middleware context-variables request-tracing

Intermediate 7 steps