# Javascript Pro

Writes, debugs, and refactors JavaScript code using modern ES2023+ features...

- Repository: https://github.com/Jeffallan/claude-skills (12164 stars)
- Category: Engineering
- License: MIT
- Last updated: 2026-10-30
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add Jeffallan/claude-skills --skill javascript-pro -g -a claude-code -y`
Codex: `npx skills add Jeffallan/claude-skills --skill javascript-pro -g -a codex -y`
Cursor: `npx skills add Jeffallan/claude-skills --skill javascript-pro -g -a cursor -y`
Gemini CLI: `npx skills add Jeffallan/claude-skills --skill javascript-pro -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add Jeffallan/claude-skills`

## Description

Writes, debugs, and refactors JavaScript code using modern ES2023+ features, async/await patterns, ESM module systems, and Node.js APIs. Use when building vanilla JavaScript applications, implementing Promise-based async flows, optimising browser or Node.js performance, working with Web Workers or Fetch API, or reviewing .js/.mjs/.cjs files for correctness and best practices.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# JavaScript Pro

## When to Use This Skill

- Building vanilla JavaScript applications
- Implementing async/await patterns and Promise handling
- Working with modern module systems (ESM/CJS)
- Optimizing browser performance and memory usage
- Developing Node.js backend services
- Implementing Web Workers, Service Workers, or browser APIs

## Core Workflow

1. **Analyze requirements**, Review `package.json`, module system, Node version, browser targets; confirm `.js`/`.mjs`/`.cjs` conventions
2. **Design architecture**, Plan modules, async flows, and error handling strategies
3. **Implement**, Write ES2023+ code with proper patterns and optimisations
4. **Validate**, Run linter (`eslint --fix`); if linter fails, fix all reported issues and re-run before proceeding. Check for memory leaks with DevTools or `--inspect`, verify bundle size; if leaks are found, resolve them before continuing
5. **Test**, Write comprehensive tests with Jest achieving 85%+ coverage; if coverage falls short, add missing cases and re-run. Confirm no unhandled Promise rejections

## Reference Guide

Load detailed guidance based on context:

| Topic | Reference | Load When |
|-------|-----------|-----------|
| Modern Syntax | `references/modern-syntax.md` | ES2023+ features, optional chaining, private fields |
| Async Patterns | `references/async-patterns.md` | Promises, async/await, error handling, event loop |
| Modules | `references/modules.md` | ESM vs CJS, dynamic imports, package.json exports |
| Browser APIs | `references/browser-apis.md` | Fetch, Web Workers, Storage, IntersectionObserver |
| Node Essentials | `references/node-essentials.md` | fs/promises, streams, EventEmitter, worker threads |

## Constraints

The rest: https://github.com/Jeffallan/claude-skills/blob/HEAD/skills/javascript-pro/SKILL.md