moai-lang-javascript

name	moai-lang-javascript
description	JavaScript ES2024+ development specialist covering Node.js 22 LTS, Bun 1.x (serve, SQLite, S3, shell, test), Deno 2.x, testing (Vitest, Jest), linting (ESLint 9, Biome), and backend frameworks (Express, Fastify, Hono). Use when developing JavaScript APIs, web applications, or Node.js projects.
license	Apache-2.0
compatibility	Designed for Claude Code
allowed-tools	Read Grep Glob Bash(node:*) Bash(npm:*) Bash(npx:*) Bash(yarn:*) Bash(pnpm:*) Bash(bun:*) Bash(deno:*) Bash(jest:*) Bash(vitest:*) Bash(eslint:*) Bash(prettier:*) Bash(biome:*) mcp__context7__resolve-library-id mcp__context7__get-library-docs
user-invocable	false
metadata	{"version":"1.2.0","category":"language","status":"active","updated":"2026-01-11","modularized":"false","tags":"language, javascript, nodejs, bun, deno, vitest, eslint, express"}
progressive_disclosure	{"enabled":true,"level1_tokens":100,"level2_tokens":5000}
triggers	{"keywords":["JavaScript","Node.js","Bun","Deno","Express","Fastify","Hono","Vitest","Jest","ESLint",".js","package.json"],"languages":["javascript","js"]}

Quick Reference (30 seconds)

JavaScript ES2024+ Development Specialist - Modern JavaScript with Node.js 22 LTS, multiple runtimes, and contemporary tooling.

Auto-Triggers: Files with .js, .mjs, or .cjs extensions, package.json, Node.js projects, JavaScript discussions

Core Stack:

• ES2024+: Set methods, Promise.withResolvers, immutable arrays, import attributes
• Node.js 22 LTS: Native TypeScript, built-in WebSocket, stable watch mode
• Runtimes: Node.js 20 and 22 LTS, Deno 2.x, Bun 1.x
• Testing: Vitest, Jest, Node.js test runner
• Linting: ESLint 9 flat config, Biome
• Bundlers: Vite, esbuild, Rollup
• Frameworks: Express, Fastify, Hono, Koa

Quick Commands:

Create a Vite project using npm create vite with latest tag, project name, and vanilla template. Initialize with modern tooling using npm init and npm install with D flag for vitest, eslint, and eslint/js. Run with Node.js watch mode using node with watch flag. Run TypeScript directly in Node.js 22+ using node with experimental-strip-types flag.

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Implementation Guide (5 minutes)

ES2024 Key Features

Set Operations:

Create setA with values 1, 2, 3, 4 and setB with values 3, 4, 5, 6. Call setA.intersection with setB to get Set containing 3 and 4. Call setA.union with setB to get Set containing 1 through 6. Call setA.difference with setB to get Set containing 1 and 2. Call setA.symmetricDifference with setB to get Set containing 1, 2, 5, and 6. Call isSubsetOf, isSupersetOf, and isDisjointFrom methods for set comparisons.

Promise.withResolvers:

Create a createDeferred function that destructures promise, resolve, and reject from Promise.withResolvers call. Return an object with these three properties. Create a deferred instance, set a timeout to resolve with done after 1000 milliseconds, and await the promise for the result.

Immutable Array Methods:

Create original array with values 3, 1, 4, 1, 5. Call toSorted to get new sorted array without mutating original. Call toReversed to get new reversed array. Call toSpliced with index 1, delete count 2, and insert value 9. Call with method at index 2 with value 99 to get new array with replaced element. The original array remains unchanged.

Object.groupBy and Map.groupBy:

Create items array with objects containing type and name properties. Call Object.groupBy with items and a function that returns item.type to get an object with arrays grouped by type. Call Map.groupBy with the same arguments to get a Map with type keys and array values.

ES2025 Features

Import Attributes for JSON Modules:

Import config from config.json with type attribute set to json. Import styles from styles.css with type attribute set to css. Access config.apiUrl property.