33-js-concepts for Claude Code: skills for the docs, not a tutor

What is leonardomso/33-js-concepts

leonardomso/33-js-concepts is a Claude Code plugin that Flowy indexes from its public GitHub repository, which carries 66,514 stars. Flowy files it under the content category, and that placement fits: everything the plugin ships is a writing and review tool, not a general JavaScript helper. It packages 6 skills and nothing else, no commands, no agents, no MCP servers, no hooks, for 6 components total.

The repository behind it is a well known list of core JavaScript concepts every developer is expected to know, each one normally written up as a page of notes with a set of external links for further reading. This plugin is not that list turned into a chat tutor. It is the authoring toolkit behind it: skills for drafting, fact-checking, testing, resource upkeep and search tuning on the concept pages themselves, built for whoever writes and maintains that documentation rather than whoever reads it.

What do the six skills do

• write-concept writes or reviews a single JavaScript concept documentation page, following the project's own structure and quality guidelines rather than an open format.
• fact-check checks a page's technical accuracy after a draft exists: its code examples, its compliance with MDN and the ECMAScript spec, and the external resources it links to.
• test-writer generates Vitest tests for the code examples on a page, following the project's own conventions and referencing the source lines each test covers.
• resource-curator finds and evaluates external resources worth linking from a concept page, and separately audits the links already on a page for ones that are broken or out of date.
• seo-review runs a focused SEO audit on a finished page: search visibility, featured snippet potential, and ranking factors, rather than its technical correctness.
• concept-workflow is the orchestrator. Its own description says it runs the other skills together, from research through to a final review, so one page can move through the whole pipeline in a single pass.

How the pieces fit together

Read as a sequence, the five specialist skills cover one page's life cycle end to end. write-concept produces or edits the draft. fact-check and test-writer both guard correctness, one against MDN and the spec, the other against whether the code examples actually run the way the page claims. resource-curator keeps the page's outbound links healthy over time, which matters for a page whose value depends on the external resources it points readers toward. seo-review reads as the last step, since tuning search visibility on a page that has not been checked for accuracy yet is work that may need redoing. concept-workflow exists so that order does not have to be remembered or run by hand on every page.

Who this plugin is for

This fits someone maintaining leonardomso/33-js-concepts itself, or a fork, or a similarly shaped reference project: a fixed set of concept pages, each with code examples, external links, and its own search surface. For that job, the six skills cover drafting, accuracy, tests, link upkeep and search visibility as one connected pipeline instead of six separate habits to remember.

It is a poor fit for a different job: asking Claude to explain a JavaScript concept in a conversation. None of the six skills answer a question in chat. Each one reads, writes, or checks a documentation page on disk, and the page is the output, not an explanation typed back at you.

How do I install it

Flowy indexes leonardomso/33-js-concepts from its public GitHub repository. Install it from the listing page linked at the top of this guide, which derives the current install command from the plugin's own manifest rather than repeating one here.