Intermediate code explainers

go

func (h *TransactionHandler) ExportCSV(c *gin.Context) {
	ctx := c.Request.Context()
	filters := parseTransactionFilters(c)

Streaming a CSV export in Gin

streaming csv-export database-cursor

Intermediate 8 steps

php

<?php
 
namespace App\Rules;

How a custom phone validation rule works in Laravel

validation custom-rules dependency

Intermediate 6 steps

ruby

class Comment < ApplicationRecord
  belongs_to :commentable, polymorphic: true, counter_cache: true
  belongs_to :author, class_name: "User"

How polymorphic comments work in Rails

polymorphic-association concerns counter-cache

Intermediate 8 steps

python

import json
import logging
 
import stripe

Handling Stripe webhooks in Django

webhooks signature-verification idempotency

Intermediate 7 steps

javascript

import { useState, useEffect, useCallback, useRef } from "react";
 
export function usePersistentForm(storageKey, initialValues) {
  const [values, setValues] = useState(() => {

A React hook that persists form state to localStorage

custom-hooks localstorage debounce

Intermediate 9 steps

rust

use axum::{extract::State, http::StatusCode, response::IntoResponse, Json};
use serde::{Deserialize, Serialize};
use uuid::Uuid;

Building a typed create_user handler in Axum

serde extractors sqlx

Intermediate 7 steps

java

@Component
public class JwtAuthenticationFilter extends OncePerRequestFilter {
 
    private final JwtTokenProvider tokenProvider;

How a JWT auth filter works in Spring

authentication jwt servlet-filter

Intermediate 8 steps

typescript

function throttle<T extends (...args: any[]) => void>(
  fn: T,
  limit: number
): (...args: Parameters<T>) => void {

Building a trailing-edge throttle in TypeScript

throttling closures generics

Intermediate 7 steps

go

package store
 
import (
	"database/sql"

Wrapping and inspecting errors in Go

error-handling error-wrapping sentinel-errors

Intermediate 8 steps

php

<?php
 
namespace App\Support;

Building a URL slug from any title in PHP

regex transliteration string-processing

Intermediate 8 steps

python

from collections import deque
 
 
class RollingAverage:

A rolling average over a fixed window

sliding-window running-sum deque

Intermediate 7 steps

javascript

function groupBy(items, keySelector) {
  const resolveKey = typeof keySelector === 'function'
    ? keySelector
    : (item) => item[keySelector];

Building a flexible groupBy in JavaScript

higher-order-functions reduce data-transformation

Intermediate 6 steps

typescript

interface TokenBucketOptions {
  capacity: number;
  refillPerSecond: number;
}

How a token bucket rate limiter works

rate-limiting token-bucket lazy-evaluation

Intermediate 7 steps

go

package main
 
import (
	"context"

Graceful HTTP shutdown in Go

graceful-shutdown signals goroutines

Intermediate 8 steps

php

<?php
 
declare(strict_types=1);

Streaming file lines with a PHP generator

generators lazy-evaluation file-io

Intermediate 7 steps

ruby

class SessionsController < ApplicationController
  MAX_ATTEMPTS = 5
  THROTTLE_WINDOW = 15.minutes

Throttling failed logins in Rails

rate-limiting authentication caching

Intermediate 7 steps

python

from collections import OrderedDict
from typing import Callable, Hashable, Iterable, Iterator, TypeVar
 
T = TypeVar("T")

Two ways to dedupe while keeping order

deduplication generators ordered-data

Intermediate 7 steps

javascript

function makeReorderableList(listEl, onReorder) {
  let draggedItem = null;
 
  listEl.addEventListener('dragstart', (e) => {

Drag-to-reorder lists with the HTML5 drag API

drag-and-drop event-delegation dom-manipulation

Intermediate 8 steps