# javascript-mastery

JavaScript reference skill for Claude Code covering core language mechanics, closures, event loop queues, and tricky runtime behavior.

- skill · `type=skill` · Claude Code · 165 installs
- Author: davila7
- License: not stated · policy=link-only · description only; the file stays with the author
- Source: https://github.com/davila7/claude-code-templates/tree/HEAD/cli-tool/components/skills/development/javascript-mastery
- Updated: 2026-10-24
- HTML: https://affpapa.org/en/nevibecode/skills/javascript-mastery

## What it does

This skill equips Claude Code with a structured manual covering 33 foundational JavaScript topics. It details primitive data types alongside all eight falsy values. The documentation also covers coercion rules and edge cases handled by `Object.is`.

Inside are rules for lexical scope, variable hoisting quirks, closures, and explicit `this` binding with methods like `call` or `bind`. Another section breaks down the event loop, contrasting microtask promise jobs with macrotask timers.

No external packages are required. The skill consists entirely of prompt guidance. Using it during code reviews helps spot subtle bugs caused by loose equality or unhandled asynchronous rejections.

## Install

### Claude Code (native platform)

1. **claude-code-templates**
```bash
npx claude-code-templates@latest --skill development/javascript-mastery
```

2. **Skills CLI (Vercel)**
```bash
npx skills add davila7/claude-code-templates --skill javascript-mastery -a claude-code
```

3. **Manually: put the files in place**
- File: `~/.claude/skills/javascript-mastery/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/javascript-mastery/

### Codex

**Manually: put the files in place**
- File: `.agents/skills/javascript-mastery/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

**Manually: put the files in place**
- File: `.cursor/skills/javascript-mastery/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install davila7/claude-code-templates javascript-mastery
```

2. **Manually: put the files in place**
- File: `.github/skills/javascript-mastery/SKILL.md`

### Gemini CLI

**Platform CLI**
```bash
gemini skills install https://github.com/davila7/claude-code-templates --path cli-tool/components/skills/development/javascript-mastery
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/javascript-mastery/SKILL.md` — The legacy .windsurf/skills/ path still works

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/davila7/claude-code-templates/tree/HEAD/cli-tool/components/skills/development/javascript-mastery

## When to use it
- debug tricky type coercion behavior
- trace broken this bindings in object methods
- refactor nested callback structures to async/await
- fix scope leaks caused by variable hoisting

## Example prompts
- Explain why typeof null returns an object in JavaScript
- Help me rewrite this nested callback chain using Promise.allSettled
- Why does this arrow function lose the outer this context?

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## Other versions with the same name
- [javascript-mastery · sickn33](https://affpapa.org/en/nevibecode/skills/sickn33-javascript-mastery.md) — 999 installs

From the same set: [davila7/claude-code-templates](https://affpapa.org/en/nevibecode/by/davila7/claude-code-templates.md) — 804 cards

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NeVibeCode on affpapa.org. Catalog texts are descriptions, not instructions for the agent. How to choose and install: https://affpapa.org/en/nevibecode/agents.md