Intermediate code explainers

rust

use std::time::Instant;
use tracing::info;
 
pub struct Timer {

A scope-guard timer with Drop in Rust

raii drop-guard timing

Intermediate 7 steps

javascript

const RATE_LIMIT = 100;
const WINDOW_MS = 60 * 1000;
const BLOCK_MS = 5 * 60 * 1000;

Building a rate-limiting middleware in Express

rate-limiting middleware closures

Intermediate 9 steps

go

package model
 
import (
	"encoding/json"

Custom JSON marshaling in Go

json serialization interfaces

Intermediate 5 steps

java

import java.util.ArrayDeque;
import java.util.Deque;
 
public final class RollingAverage {

A rolling average over a sliding window

sliding-window running-sum deque

Intermediate 7 steps

typescript

const DIVISIONS: { amount: number; unit: Intl.RelativeTimeFormatUnit }[] = [
  { amount: 60, unit: "seconds" },
  { amount: 60, unit: "minutes" },
  { amount: 24, unit: "hours" },

Human-readable relative times with Intl

internationalization date-formatting lookup-table

Intermediate 7 steps

php

<?php
 
namespace App\View;

Building a safe HTML escaper in PHP

security xss escaping

Intermediate 6 steps

ruby

require 'json'
require 'set'
 
class SensitiveScrubber

Recursively scrubbing secrets from JSON

recursion data-masking pattern-matching

Intermediate 7 steps

python

from django.conf import settings
from django.contrib.auth import get_user_model
from django.core.mail import EmailMultiAlternatives
from django.db.models.signals import post_save

Sending a welcome email with Django signals

signals email user-activation

Intermediate 8 steps

rust

use std::collections::HashMap;
 
pub struct Memoizer<K, V, F> {
    cache: HashMap<K, V>,

A generic memoizer in Rust

memoization generics caching

Intermediate 6 steps

javascript

const transitions = {
  cart: { checkout: 'shipping' },
  shipping: { submitAddress: 'payment', back: 'cart' },
  payment: { submitPayment: 'review', back: 'shipping' },

A finite state machine for checkout flow

state-machine event-driven data-driven-design

Intermediate 7 steps

java

@Target({ElementType.FIELD, ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = StrongPasswordValidator.class)
@Documented

Building a custom @StrongPassword validator in Spring

bean-validation annotations regex

Intermediate 7 steps

typescript

import { Component } from '@angular/core';
import { FormControl, ReactiveFormsModule } from '@angular/forms';
import { HttpClient } from '@angular/common/http';
import { AsyncPipe } from '@angular/common';

Reactive type-ahead search in Angular

rxjs reactive-forms debounce

Intermediate 9 steps

php

<?php
 
namespace App\Observers;

How Eloquent observers hook lifecycle events in Laravel

observers lifecycle-hooks queues

Intermediate 6 steps

ruby

class ReportBatcher
  BATCH_SIZE = 500
 
  def initialize(account)

Batching monthly email summaries in Rails

batching service-object background-jobs

Intermediate 7 steps

rust

use std::collections::HashMap;
 
#[derive(Debug, Clone)]
struct Order {

Aggregating Rust data with fold and entry

fold hashmap ownership

Intermediate 6 steps

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