Intermediate code explainers

typescript

import {
  CanActivate,
  ExecutionContext,
  Injectable,

Role-based access with a NestJS guard

authorization guards decorators

Intermediate 6 steps

ruby

require "base64"
require "json"
 
module Attachment

Packing binary attachments into JSON

serialization base64 json

Intermediate 8 steps

rust

use std::sync::mpsc;
use std::thread;
use std::time::Duration;

Running work with a timeout in Rust

concurrency channels timeout

Intermediate 7 steps

javascript

function initCharacterCounter(textarea, options = {}) {
  const maxLength = options.maxLength ?? 280;
  const warnThreshold = options.warnThreshold ?? 0.9;

A live character counter for textareas

dom closures accessibility

Intermediate 7 steps

php

<?php
 
namespace App\Services;

Computing rolling averages in Laravel

rolling-average date-ranges collections

Intermediate 8 steps

python

from django.db.models import Q
 
from .models import Order

DISTINCT ON queries in Django

orm querysets postgresql

Intermediate 7 steps

go

package cache
 
import (
	"sync"

A thread-safe TTL cache in Go

concurrency mutex caching

Intermediate 9 steps

typescript

import { Injectable, computed, effect, signal } from '@angular/core';
 
export interface CartLine {
  id: string;

A signal-based cart store in Angular

signals reactivity computed-state

Intermediate 8 steps

ruby

require "yaml"
 
class FrontMatter
  DELIMITER = /\A---\s*\n(.*?)\n---\s*\n?(.*)\z/m

Parsing YAML front matter in Ruby

parsing regular-expressions yaml

Intermediate 8 steps

rust

use axum::{extract::State, response::IntoResponse, Json};
use serde::{Deserialize, Serialize};
use serde_json::{json, Value};
use std::sync::Arc;

Building a JSON-RPC 2.0 handler in Axum

json-rpc serde request-dispatch

Intermediate 8 steps

java

public List<int[]> merge(int[][] intervals) {
    if (intervals.length == 0) {
        return new ArrayList<>();
    }

Merging overlapping intervals in Java

intervals sorting greedy

Intermediate 7 steps

javascript

function autoResizeTextarea(textarea, { maxHeight = Infinity } = {}) {
  const resize = () => {
    textarea.style.height = 'auto';
    const contentHeight = textarea.scrollHeight;

Auto-resizing a textarea to fit its content

dom event-listener cleanup

Intermediate 7 steps

typescript

import { Component, signal } from '@angular/core';
import { CommonModule } from '@angular/common';
import { RevenueChartComponent } from './revenue-chart.component';
import { ReportService, RevenueReport } from './report.service';

Deferred chart loading with @defer in Angular

lazy-loading signals dependency-injection

Intermediate 8 steps

javascript

const zxcvbn = require('zxcvbn');
 
const STRENGTH_LABELS = ['Very weak', 'Weak', 'Fair', 'Strong', 'Very strong'];
const STRENGTH_COLORS = ['#d64545', '#e0803c', '#d9c94c', '#5aa84f', '#2f8f3a'];

Building a live password strength meter

debounce closures dom-events

Intermediate 8 steps

typescript

export const OrderStatus = {
  Pending: 'pending',
  Paid: 'paid',
  Shipped: 'shipped',

A type-safe order state machine in TypeScript

state-machine union-types type-guards

Intermediate 8 steps

python

import signal
import time
import logging

Graceful shutdown in a queue worker

signals graceful-shutdown message-queue

Intermediate 7 steps

javascript

function usePagination(items, pageSize = 10) {
  let currentPage = 1;
  const totalPages = Math.max(1, Math.ceil(items.length / pageSize));

A closure-based pagination helper in JS

closures encapsulation factory-function

Intermediate 9 steps

typescript

export async function copyToClipboard(text: string): Promise<boolean> {
  if (navigator.clipboard && window.isSecureContext) {
    try {
      await navigator.clipboard.writeText(text);

Clipboard copy with a legacy fallback

clipboard feature-detection graceful-degradation

Intermediate 7 steps