javascript
JavaScript Array Grouping: Object.groupBy Explained
Object.groupBy and Map.groupBy end the reduce()-based grouping pattern developers have hand-written for...
React TypeScript JavaScript
Write better
React & TypeScript.
Practical, in-depth guides on React, TypeScript, and modern frontend development - written by engineers, for engineers.
79 Articles
8 Topics
Free Always
Check your TypeScript 7 readiness
All free tools →TypeScript 7 removed flags that TypeScript 6 only warned about, so the upgrade usually fails on config rather than on code. Which makes it a thing you can check in about ten seconds instead of reading about for an hour. Want the guide first instead? The TypeScript 7 migration guide walks the whole path, and the TypeScript 7 hub orders all eleven articles the way a real migration happens.
Paste it below for an instant readiness score against everything TypeScript 7 removed or changed. Runs in your browser, nothing is uploaded.
Need to check package.json too, or want the full breakdown? Use the full TypeScript 7 Migration Readiness Checker.
- tsconfig.json generator Pick a preset - strict app, Node library, monorepo, bundler - and copy a ready compilerOptions block.
- JSON to TypeScript Paste a response, get clean interfaces. Nested objects, arrays, optional fields, and unions all handled.
- Lint coverage audit A CLI script that finds the files ESLint never opens and the CI step that cannot actually fail.
// free download
Get the TypeScript cheat sheet
Two printable pages. One email a week, no filler.
// browse by topic
Pick your rabbit hole.
Seven tracks plus the component catalog. Counts are read from the content collection at build time, so an empty track is an honest empty track.
UI Catalog
Best React & TypeScript component libraries ranked by npm downloads and GitHub stars.
24 packagesReact
Hooks, Server Components, React 19 actions, and component patterns.
13 articlesTypeScript
Generics, utility types, conditional types, and type-safe APIs.
24 articlesJavaScript
Modern ES2024+ features, async/await patterns, and runtime quirks.
6 articlesCSS
Container queries, cascade layers, custom properties, and layouts.
8 articlesPerformance
Core Web Vitals, bundle splitting, rendering strategies, and profiling.
4 articlesTooling
Vite, ESLint, TypeScript config, Vitest, and developer experience.
16 articlesProgramming with AI
Claude Code, Claude Agent SDK, MCP, AI code review, and agent workflows for TypeScript.
11 articlesLatest articles
All articles → 
typescript
TypeScript 7 Bundlers: Vite, webpack, esbuild and More
Does TypeScript 7 break your bundler? Mostly no. The split that matters...
tooling
Vitest 5 Migration Guide: What Breaks and How to Fix
Vitest 5.0.0 shipped on September 3, 2026. Here is every breaking change...
// free download
The TypeScript cheat sheet.
Utility types, conditional types, and every TS 5.x and 6.0 addition worth knowing, on two printable pages. One email a week, no filler.