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javascript
function useHashState(key, defaultValue) { const parse = () => { const params = new URLSearchParams(window.location.hash.slice(1)); return params.has(key) ? params.get(key) : defaultValue;
A React hook backed by the URL hash
custom-hooks
url-state
event-listeners
Intermediate
6 steps
typescript
import { Module } from '@nestjs/common'; import { ConfigModule, ConfigService } from '@nestjs/config'; import { createClient, RedisClientType } from 'redis';
Provide a Redis client with a NestJS factory
dependency-injection
async-factory
redis
Intermediate
6 steps
rust
pub fn collapse_whitespace(input: &str) -> String { let mut result = String::with_capacity(input.len()); let mut in_whitespace = false;
Collapsing runs of whitespace in Rust
string-processing
state-machine
iteration
Beginner
5 steps
python
from werkzeug.routing import BaseConverter, ValidationError from flask import Flask, jsonify, abort
Custom URL converters in Flask
url-routing
validation
converters
Intermediate
6 steps
java
public final class BomAwareReader { private static final char UTF8_BOM = '\uFEFF';
Skipping the UTF-8 byte-order mark in Java
file-io
encoding
byte-order-mark
Intermediate
6 steps
php
<?php namespace App\Http\Support;
Adding RFC 5988 Link headers in Laravel
pagination
http-headers
rest-api
Intermediate
7 steps
ruby
module Authenticatable extend ActiveSupport::Concern included do
JWT authentication as a Rails concern
authentication
jwt
concerns
Intermediate
6 steps
typescript
type RGB = { r: number; g: number; b: number }; type WCAGLevel = "AA" | "AAA"; type TextSize = "normal" | "large";
Checking WCAG color contrast in TypeScript
accessibility
color-math
type-safety
Intermediate
10 steps
rust
use axum::{ http::{header, StatusCode}, response::{IntoResponse, Response}, Json,
Turning errors into RFC 7807 responses in Axum
error-handling
enums
trait-implementation
Intermediate
7 steps
go
package middleware import ( "bytes"
Idempotent requests in Gin with Redis
idempotency
caching
middleware
Advanced
10 steps
javascript
function hexToRgb(hex) { const normalized = hex.replace(/^#/, ''); const full = normalized.length === 3 ? normalized.split('').map((c) => c + c).join('')
Building a two-way color picker in JS
bitwise
dom-events
data-conversion
Intermediate
9 steps
python
from typing import List, Tuple def merge_intervals(intervals: List[Tuple[int, int]]) -> List[Tuple[int, int]]:
How interval merging works
sorting
greedy
intervals
Intermediate
6 steps
java
public final class HmacJwt { private static final ObjectMapper MAPPER = new ObjectMapper(); private static final Base64.Encoder ENCODER = Base64.getUrlEncoder().withoutPadding();
How HMAC-signed JWTs are created and verified
jwt
hmac
cryptography
Intermediate
9 steps
php
<?php declare(strict_types=1);
Streaming a fixed-width file into typed objects
generators
value-objects
file-parsing
Intermediate
8 steps
ruby
class Pipeline def initialize @middlewares = [] end
Building a middleware pipeline in Ruby
closures
middleware
composition
Advanced
8 steps
typescript
import { Pipe, PipeTransform, Inject, LOCALE_ID } from '@angular/core'; interface MoneyOptions { currency?: string;
Building a cached money pipe in Angular
pipes
memoization
internationalization
Intermediate
8 steps
rust
use serde::{Deserialize, Serialize}; #[derive(Debug, Serialize, Deserialize)] pub struct UserProfile {
Trimming JSON output with serde attributes
serialization
json
attributes
Intermediate
8 steps
go
package middleware import ( "context"
A deadline-enforcing HTTP middleware in Go
middleware
context
goroutines
Advanced
7 steps