Intermediate code explainers

typescript

import slugify from "slugify";
 
interface SlugRepository {
  exists(slug: string): Promise<boolean>;

Generating unique URL slugs from titles

slugs normalization uniqueness

Intermediate 6 steps

rust

pub fn levenshtein(a: &str, b: &str) -> usize {
    let a: Vec<char> = a.chars().collect();
    let b: Vec<char> = b.chars().collect();

Levenshtein distance with two rows in Rust

dynamic-programming edit-distance space-optimization

Intermediate 6 steps

java

@Configuration
public class UserImportJobConfig {
 
    @Bean

How a Spring Batch CSV import job is wired

batch processing chunk oriented fault tolerance

Intermediate 10 steps

ruby

module FixedWidthParser
  FIELDS = [
    { name: :record_type, range: 0...2 },
    { name: :account_id,  range: 2...12, type: :integer },

Parsing fixed-width records in Ruby

parsing data-driven-design type-coercion

Intermediate 5 steps

python

from django.core.paginator import Paginator
from django.shortcuts import render
 
from .models import Product

Filtering and paginating a Django product list

queryset pagination filtering

Intermediate 7 steps

go

package handlers
 
import (
	"encoding/json"

Parsing search query params in a Go handler

http-handlers input-validation defaults

Intermediate 7 steps

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

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

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