Intermediate code explainers

go

package debounce
 
import (
	"sync"

Building a debouncer in Go

concurrency debounce timers

Intermediate 6 steps

typescript

import { useState, useEffect, useRef, useCallback } from "react";
 
interface SearchResult {
  id: string;

A debounced search hook in React

debounce custom-hooks abortcontroller

Intermediate 7 steps

java

@WebMvcTest(OrderController.class)
class OrderControllerTest {
 
    @Autowired

Slice testing a controller with @WebMvcTest in Spring

testing mocking http

Intermediate 8 steps

python

import gzip
from pathlib import Path
from typing import Iterator

Streaming TSV records with Python generators

generators lazy-evaluation file-io

Intermediate 5 steps

php

<?php
 
namespace App\Http\Requests;

How a Laravel FormRequest validates input

validation form-request input-sanitization

Intermediate 6 steps

rust

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

How a JWT extractor works in Axum

authentication jwt extractors

Intermediate 8 steps

javascript

import { useMemo, useState } from 'react';
 
function ProductList({ products }) {
  const [query, setQuery] = useState('');

Memoizing a filtered list in React

memoization derived-state filtering

Intermediate 8 steps

ruby

module Fibonacci
  CACHE = Hash.new do |cache, n|
    cache[n] = cache[n - 1] + cache[n - 2]
  end

Memoizing Fibonacci with a Hash default block

memoization recursion hash-default

Intermediate 5 steps

go

package retry
 
import (
	"context"

Retry with exponential backoff in Go

retry exponential-backoff jitter

Intermediate 8 steps

typescript

type SignupInput = {
  email: string;
  password: string;
  confirmPassword: string;

How a typed signup validator collects errors

form-validation type-safety regex

Intermediate 9 steps

java

public final class BusinessDays {
 
    private BusinessDays() {
    }

Counting business days between two dates in Java

date arithmetic utility class streams

Intermediate 7 steps

python

import hashlib
import hmac
import os

Verifying signed payment webhooks in Flask

hmac webhooks signature verification

Intermediate 7 steps

php

<?php
 
final class CsrfGuard
{

Building a per-form CSRF guard in PHP

csrf security sessions

Intermediate 8 steps

php

<?php
 
namespace App\Models;

Polymorphic comments in Laravel with morphTo

polymorphism eloquent relationships

Intermediate 5 steps

java

import java.time.Duration;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;

A safe recurring heartbeat scheduler in Java

concurrency scheduling thread-safety

Intermediate 6 steps

javascript

function initLazyLoad(root = document) {
  const images = root.querySelectorAll('img[data-src]');
 
  if (!('IntersectionObserver' in window)) {

How lazy image loading works

lazy-loading intersectionobserver progressive-enhancement

Intermediate 8 steps

go

package main
 
import (
	"bufio"

Counting matching lines in Go with bufio

file-io buffered-scanning error-handling

Intermediate 4 steps

ruby

class EventEmitter
  def initialize
    @listeners = Hash.new { |hash, key| hash[key] = [] }
  end

Building an EventEmitter in Ruby

pub-sub closures callbacks

Intermediate 7 steps