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javascript-mastery · davila7 — Claude Code skill: what it does, how to install

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

Install into Claude Code · claude-code-templates All methods and platforms ↓ 
npx claude-code-templates@latest --skill development/javascript-mastery
Open on GitHub

What javascript-mastery 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.

What it helps with

  • 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 for the agent

  • 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?

How to install javascript-mastery

1claude-code-templates

npx claude-code-templates@latest --skill development/javascript-mastery

2Skills CLI (Vercel)

npx skills add davila7/claude-code-templates --skill javascript-mastery -a claude-code

3Manually: put the files in place

~/.claude/skills/javascript-mastery/SKILL.md

Copy the whole skill folder; for one project use .claude/skills/javascript-mastery/

Step by step, with commands for each platform: How to install skills in Claude Code: five ways

Questions about javascript-mastery

How to install javascript-mastery in Claude Code?

Run npx claude-code-templates@latest --skill development/javascript-mastery in your terminal. Alternatively, place the file at ~/.claude/skills/javascript-mastery/SKILL.md.

What does javascript-mastery do?

It provides the agent with an exact language reference to help debug quirks, explain fundamentals, and check code against best practices.

Which topics are covered in the guide?

The material covers primitive types, closures, hoisting mechanisms, event loop execution order, and promise combinator patterns.

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