Skip to content
Get packs

Prefer const and let over var

Reviews and rewrites JavaScript to replace var with const or let, explaining scope and hoisting fixes.

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

What it does

When installed, the agent gets a checklist-style guide for a common JavaScript best practice: replacing the old var keyword with const (for values that never change) or let (for values that do). Asked to check a file, it flags every var with line numbers, rewrites them, and explains the scope, hoisting, and temporal dead zone reasons behind the change. It also reviews scripts and browser-side code for related issues and suggests how to verify fixes in a browser.

Great for

  • Developers cleaning up older JavaScript that still uses var
  • Students learning the difference between var, let, and const
  • Code reviewers who want a consistent checklist for this rule

Skip it if

  • Projects that need a full, automated linter run; the skill reviews by reading code, not by running tooling, so it may miss occurrences in large codebases
  • Reviews of performance bottlenecks or bugs in code that does not use var; the browser-review instructions are broad and can produce generic advice

Try asking

  • “Check this JavaScript file for any var declarations and list them with line numbers.”
  • “Replace all var declarations in this script with const or let as appropriate.”
  • “Explain why const and let are preferred over var, including the temporal dead zone.”
  • “Review this client component for code that violates the const/let rule and suggest how to verify the change in the browser.”
Step-by-step guide: how to use Prefer const and let over varInstall, 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.

    const-let.zip
  2. 2

    Add it to your agent

    Claude Code (all projects)

    mkdir -p ~/.claude/skills && unzip const-let.zip -d ~/.claude/skills/

    Claude Code / Agent SDK (this project only)

    mkdir -p .claude/skills && unzip const-let.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

  • Paste or point to the specific file so the agent can give exact line numbers for var uses.
  • Ask for a before-and-after diff so you can review each change before accepting it.
  • Remember that const prevents reassignment but not mutation of objects and arrays; check that your intent matches.

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.