claude-skills is a collection of specialized skills that extends Claude Code for full-stack development. Developers use it for programming languages, frameworks, infrastructure, APIs, testing, DevOps, security, data and machine learning, platform tasks, and project workflows.
Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add Jeffallan/claude-skills --skill javascript-progit clone --depth 1 https://github.com/Jeffallan/claude-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/jeffallan/claude-skills/javascript-pro)<a href="https://agentmods.dev/skills/jeffallan/claude-skills/javascript-pro"><img src="https://agentmods.dev/badge/skills/jeffallan/claude-skills/javascript-pro/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/jeffallan/claude-skills/javascript-pro"><img src="https://agentmods.dev/badge/skills/jeffallan/claude-skills/javascript-pro.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket warn
- Snyk pass
- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00084 | $0.01194 |
| Opus 5.5 | $0.00034 | $0.00478 |
| Sonnet 5.5 | $0.00017 | $0.00239 |
| Haiku 4.5 | $0.00008 | $0.00119 |
Grade A, and why
javascript-pro scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 18d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
Copies of this mod
4 near-identical copies found in the catalogue:
- javascript-pro — 100% identical, 3 lines differ
- javascript-pro — 97% identical, 5 lines differ
- javascript-pro — 97% identical, 5 lines differ
- javascript-pro — 97% identical, 5 lines differ
How it starts
The opening of the file, as written. The whole thing — 138 lines — stays where its author put it; the contents beside it link to each section on GitHub.
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
- Analyze requirements — Review
package.json, module system, Node version, browser targets; confirm.js/.mjs/.cjsconventions - Design architecture — Plan modules, async flows, and error handling strategies
- Implement — Write ES2023+ code with proper patterns and optimisations
- 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 - 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
MUST DO
- Use ES2023+ features exclusively
- Use
X | nullorX | undefinedpatterns - Use optional chaining (
?.) and nullish coalescing (??) - Use async/await for all asynchronous operations
- Use ESM (
import/export) for new projects - Implement proper error handling with try/catch
- Add JSDoc comments for complex functions
- Follow functional programming principles
What ships with it
5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 18d ago Changed · +3 lines 861bcf73723a
- 1mo ago First seen · 135 lines · 84 tokens per session scan A fb73d0545452
javascript-pro is a skill published in the GitHub repository Jeffallan/claude-skills (11,987 stars, last pushed today), licensed MIT. It adds 84 tokens to every session and 1,194 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
dotnet-architecture
Guides implementation of Clean Architecture in .NET projects. Covers all layers: DTO, Domain (Models, Services, Enums), Infra.Interfaces (Repository, AppServices), Infra (Context, Repository, AppServices), and Application (DI/Startup). Use when creating entities, services, repositories, or restructuring architecture.…
dotnet-graphql
Guides implementation of GraphQL with HotChocolate in .NET 8 projects following Clean Architecture. Creates the GraphQL project with single or multi-schema design, queries returning IQueryable for EF Core optimization, type extensions for computed fields, field hiding, error logging, and DI registration. Use when…
dotnet-multi-tenant
Implements Multi-Tenant pattern in .NET APIs with per-tenant database isolation, per-tenant JWT secrets, ACL layer with automatic TenantId propagation via DelegatingHandler, and dynamic DbContext factory. Covers TenantMiddleware, TenantContext, TenantResolver, TenantHeaderHandler, TenantDbContextFactory, and dynamic…
nnews-guide
Guides how to integrate the NNews NuGet package for consuming the NNews CMS API in a .NET 8 project. Use when the user wants to consume articles, categories, tags, images, or AI-powered content generation from the NNews API.
ztools-guide
Guides how to integrate the zTools package for ChatGPT, DALL-E image generation, file upload (S3), slug generation, email sending, and document validation in a .NET 8 project. Use when the user wants to use AI features, upload files, generate slugs, send emails, or understand zTools integration.
dotnet-doc-controller
Generates comprehensive API documentation for a .NET REST controller. Use when the user wants to document API endpoints, generate controller docs, or create API reference documentation.