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Duplicate JavaScript Auditor

Finds and flags duplicate JavaScript libraries slowing down a web page, with guidance on fixing them

Source Download skill
Repository
thedaviddias/Front-End-Checklist
Stars
74,632
Licence
MIT
Files
2 files

What it does

When installed, this skill tells the AI agent to review a website for cases where the same JavaScript library is loaded more than once, or in multiple versions, which makes pages heavier and can cause conflicts. The agent is guided to confirm the problem using tools such as Lighthouse, DevTools or bundle analysis before suggesting changes, and to explain the performance impact and how to consolidate to one version. It is a checklist-style guide from the Front-End Checklist project, not a tool that runs tests by itself.

Great for

  • Front-end developers trying to speed up a slow website
  • Teams reviewing third-party scripts that bring in their own copies of common libraries
  • Anyone preparing a performance audit who wants a structured checklist for duplicate code

Skip it if

  • Projects with no web front-end, since the guidance is about browser JavaScript loading (not useful for backend-only code)
  • Automated fixes without review: the skill recommends consolidating dependencies, which can break behaviour if versions differ, so changes should be tested first

Try asking

  • “Audit my site for duplicate JavaScript libraries that are slowing down page loads”
  • “Check whether jQuery is being loaded twice on my pages and explain the impact”
  • “Review our third-party scripts for redundant bundled dependencies”
  • “Explain to my team why multiple versions of the same library hurt performance”
Step-by-step guide: how to use Duplicate JavaScript AuditorInstall, first run, examples, tips and FAQs

Install in 3 steps

  1. 1

    Download the skill

    The ZIP contains the 2 original files, the MIT licence and an attribution note.

    duplicate-js.zip
  2. 2

    Add it to your agent

    Claude Code (all projects)

    mkdir -p ~/.claude/skills && unzip duplicate-js.zip -d ~/.claude/skills/

    Claude Code / Agent SDK (this project only)

    mkdir -p .claude/skills && unzip duplicate-js.zip -d .claude/skills/

    Claude apps (web/desktop): Settings → Capabilities → Skills → Upload skill, and choose the ZIP.

  3. 3

    Ask for the task

    No special command needed — the agent reads the skill's description and loads it when your request matches. Try one of the prompts above.

Get better results

  • Give the agent real measurements (Lighthouse report, DevTools network tab, or bundle analyser output) so it can verify the bottleneck rather than guess.
  • Point it at specific pages or files, since the guidance asks for exact files and requests to be flagged.
  • Ask for the consolidation plan first and test each dependency change, because merging library versions can cause unexpected behaviour.

What's inside

  • references/rule.md
  • SKILL.md

Redistributed unmodified from thedaviddias/Front-End-Checklist under the MIT licence. The assessment was drafted with AI from the skill's files on 2026-10-29. Skills can instruct your agent to run code — read SKILL.md and any scripts before installing.