Code Explainers

Browse the library

typescript
import { Controller, Get, Param, Post, Body, Version, VERSION_NEUTRAL } from '@nestjs/common';
import { UsersService } from './users.service';
import { CreateUserDto } from './dto/create-user.dto';
 

How API versioning works in NestJS

api-versioning routing dependency-injection
Intermediate 9 steps
javascript
import { useState, useRef, useCallback, useLayoutEffect } from "react";
 
export function useResizeObserver({ debounce = 0 } = {}) {
  const [size, setSize] = useState({ width: 0, height: 0 });

A resize-observing hook in React

custom-hook resizeobserver callback-ref
Advanced 8 steps
rust
use std::io::{BufRead, BufReader};
use std::process::{Command, Stdio};
 
#[derive(Debug)]

Parsing ps output into structs in Rust

subprocess parsing iterators
Intermediate 8 steps
go
package handlers
 
import (
	"net/http"

Validating query params with Gin binding tags

validation struct-tags pagination
Intermediate 8 steps
php
<?php
 
namespace App\Http\Resources;
 

Shaping API JSON with a Laravel Resource

api serialization data transformation
Intermediate 7 steps
ruby
class InventoryItem < ApplicationRecord
  belongs_to :warehouse
 
  validates :quantity, numericality: { greater_than_or_equal_to: 0 }

Safe inventory updates in Rails

concurrency pessimistic-locking optimistic-locking
Advanced 7 steps
java
package com.example.inventory;
 
import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVParser;

Reading and writing CSV with Commons CSV

csv-parsing file-io try-with-resources
Intermediate 7 steps
python
from fastapi import APIRouter, FastAPI, HTTPException
from pydantic import BaseModel
 
 

Versioning a FastAPI API with mounted sub-apps

api-versioning response-models sub-applications
Intermediate 6 steps
typescript
import { HttpService } from '@nestjs/axios';
import { Injectable, Logger, ServiceUnavailableException } from '@nestjs/common';
import { AxiosError } from 'axios';
import { catchError, firstValueFrom, retry, timer } from 'rxjs';

Resilient payment retries in NestJS

retry exponential-backoff rxjs
Advanced 8 steps
javascript
import { useState } from "react";
 
const EMAIL_RE = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
 

Building a validated signup form in React

form-validation controlled-components state-management
Intermediate 10 steps
go
package api
 
import (
	"encoding/json"

Building reusable JSON helpers in Go HTTP handlers

http json error-handling
Intermediate 9 steps
java
package com.example.security;
 
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;

Salted password hashing with PBKDF2 in Java

password-hashing pbkdf2 salting
Intermediate 7 steps
typescript
interface PaginationParams {
  totalItems: number;
  pageSize: number;
  currentPage: number;

Building safe pagination metadata in TypeScript

pagination input-validation pure-functions
Intermediate 7 steps
php
final class DebouncedSessionStore
{
    private array $pending = [];
    private array $timers = [];

Debouncing session writes with an event loop

debounce event-loop atomic-write
Advanced 9 steps
ruby
require "forwardable"
 
class ShoppingCart
  extend Forwardable

Delegation in Ruby with Forwardable

delegation composition enumerable
Intermediate 9 steps
javascript
import { useRef, useState, useCallback, useMemo } from 'react';
 
export function VirtualList({ items, rowHeight = 40, height = 600, overscan = 5, renderRow }) {
  const [scrollTop, setScrollTop] = useState(0);

How a virtualized list works in React

virtualization performance memoization
Intermediate 8 steps
rust
use axum::{
    routing::get,
    Json, Router,
};

Response compression in Axum with tower-http

middleware compression http
Intermediate 6 steps
go
package server
 
import (
	"net/http"

Serving cached static assets in Gin

caching static-files middleware
Intermediate 7 steps