Code Explainers
Browse the library
rust
use std::sync::{mpsc, Arc, Mutex}; use std::thread; use std::time::Duration;
Building a thread pool in Rust
concurrency
channels
thread-pool
Advanced
9 steps
python
from collections.abc import Mapping from typing import Any, Iterator
Flattening nested config into dotted keys
recursion
generators
tree-traversal
Intermediate
7 steps
ruby
module DurationFormatter UNITS = [ ['week', 604_800], ['day', 86_400],
Turning seconds into human-readable durations in Ruby
greedy-decomposition
modular-arithmetic
formatting
Intermediate
7 steps
javascript
const express = require('express'); const v1 = express.Router();
Versioning an API with Express Routers
api versioning
routing
modularity
Intermediate
10 steps
java
public class SortedListMerger { public static int[] merge(int[] a, int[] b) { int[] result = new int[a.length + b.length];
Merging two sorted arrays in Java
two-pointers
merging
arrays
Beginner
6 steps
php
<?php namespace App\Support;
Merging query params onto a URL in PHP
url-parsing
query-strings
immutability
Intermediate
8 steps
typescript
import { Pipe, PipeTransform, ChangeDetectorRef, NgZone, OnDestroy } from '@angular/core'; @Pipe({ name: 'timeAgo',
A self-refreshing timeAgo pipe in Angular
impure-pipe
change-detection
timers
Advanced
10 steps
python
import csv import io from datetime import datetime
Streaming a CSV export in Flask
streaming
generators
csv
Intermediate
9 steps
go
package cache import ( "container/list"
Building a generic LRU cache in Go
lru-cache
generics
linked-list
Intermediate
8 steps
php
<?php class ImageUploadService {
Validating file uploads safely in PHP
file-upload
input-validation
security
Intermediate
8 steps
ruby
class Comment < ApplicationRecord belongs_to :post belongs_to :author, class_name: "User"
Live-updating comments with Turbo in Rails
turbo-streams
callbacks
associations
Intermediate
8 steps
python
import time from collections import defaultdict from threading import Lock
Sliding-window login rate limiting in Flask
rate-limiting
sliding-window
thread-safety
Intermediate
7 steps
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