Code Explainers

Browse the library

typescript 
import { Component, computed, signal } from '@angular/core';
import { CdkTableModule } from '@angular/cdk/table';
import { CdkScrollableModule } from '@angular/cdk/scrolling';
 

Paginating a CDK table with Angular signals

signals computed-state pagination
Intermediate 9 steps
ruby 
require "csv"
 
class CsvExporter
  def initialize(records, columns: nil)

Turning records into CSV in Ruby

csv data-export serialization
Intermediate 7 steps
javascript 
async function uploadInBatches(records, uploadFn, { batchSize = 100, concurrency = 3 } = {}) {
  const batches = [];
  for (let i = 0; i < records.length; i += batchSize) {
    batches.push(records.slice(i, i + batchSize));

Uploading records with bounded concurrency

concurrency worker-pool async-await
Advanced 8 steps
python 
from copy import deepcopy
 
 
class CowSnapshot:

Copy-on-write attribute snapshots in Python

copy-on-write descriptors attribute-interception
Advanced 7 steps
java 
package com.example.validation;
 
import java.util.List;
import java.util.stream.Collectors;

Validating JSON payloads against a schema in Java

json-schema validation recursion
Intermediate 8 steps
rust 
use std::collections::HashMap;
 
fn decode_component(input: &str) -> String {
    let bytes = input.as_bytes();

Parsing a URL query string in Rust

url-encoding byte-parsing iterators
Intermediate 8 steps
go 
func ListProducts(c *gin.Context) {
	allowed := map[string]string{
		"category": "category",
		"brand":    "brand",

Safe query filtering in a Gin handler

input-validation whitelisting query-building
Intermediate 7 steps
php 
<?php
 
namespace App\RateLimiting;
 

Sliding-window rate limiting with Redis sorted sets

rate-limiting redis sorted-sets
Advanced 8 steps
typescript 
type Semver = {
  major: number;
  minor: number;
  patch: number;

Parsing and comparing semver strings in TypeScript

parsing regular-expressions comparison
Intermediate 9 steps
ruby 
class CircuitBreaker
  class OpenCircuitError < StandardError; end
 
  def initialize(failure_threshold: 5, reset_timeout: 30, half_open_max: 1)

How a circuit breaker guards failing calls

state-machine fault-tolerance concurrency
Advanced 9 steps
javascript 
function formatPhoneNumber(value) {
  const digits = value.replace(/\D/g, '').slice(0, 10);
  const parts = [];
 

Building a live phone number input mask

input-masking regex dom-events
Intermediate 7 steps
python 
from flask import Blueprint, jsonify
from marshmallow import Schema, fields, validate, EXCLUDE
from webargs.flaskparser import use_args
 

Validating query params in Flask with webargs

validation schema query-building
Intermediate 10 steps
java 
public URI buildSearchUri(String query, int page, int size, List<String> tags) {
    UriComponentsBuilder builder = UriComponentsBuilder
            .fromUriString("https://api.example.com")
            .path("/v2/products/search")

Building URIs safely with UriComponentsBuilder in Spring

url-building builder-pattern encoding
Intermediate 5 steps
rust 
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum FileKind {
    Png,
    Jpeg,

Detecting file types by magic bytes in Rust

pattern-matching byte-slices lookup-table
Intermediate 7 steps
go 
func (h *ExportHandler) BulkExport(c *gin.Context) {
	projectID := c.Param("projectID")
 
	reports, err := h.reports.ListByProject(c.Request.Context(), projectID)

Streaming a ZIP download in Gin

streaming zip-archive http-headers
Intermediate 8 steps
php 
<?php
 
namespace App\Models\Concerns;
 

How an Auditable trait logs Eloquent changes in Laravel

traits model-events polymorphic-relations
Intermediate 8 steps
php 
<?php
 
namespace App\Http\Controllers;
 

Server-Sent Events in Laravel

server-sent-events streaming long-polling
Advanced 9 steps
java 
@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {
 

Real-time chat over STOMP WebSockets in Spring

websockets stomp messaging
Intermediate 8 steps