Const Let
Testing & Qualityconst-letConst Let is an Agent Skill for testing & quality published in the thedaviddias/Front-End-Checklist repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.
Use when reviewing scripts, client components, bundles, or runtime behavior related to Prefer const and let over var. Inspect both source code and the browser execution path so fixes target the real bottleneck or bug.
How to use this skill
Bring this guide into your coding agent with a prompt tailored to the tool you use.
- Open your project in Codex.
- Copy and paste the prompt below.
- Review files and risks before approving any action.
Inspect the Agent Skill at https://github.com/thedaviddias/Front-End-Checklist/blob/HEAD/skills/const-let/SKILL.md and all supporting files. Report provenance, permissions, scripts, dependencies, and security risks. Propose an exact installation into .agents/skills/const-let, but wait for my approval before writing files or running scripts.
Copying this prompt does not install or run the skill. Review third-party files before use.
Prefer const and let over var
var's function scope and hoisting behavior regularly causes bugs where variables are accessible outside the block they were declared in. const and let enforce block scope and make code intent clearer — const signals that a binding should not be reassigned, which helps readers understand data flow.
Quick Reference
- Use const for values that are never reassigned
- Use let when reassignment is needed
- Never use var — it has function scope and is hoisted, causing subtle bugs
- const does not mean immutable — objects and arrays declared with const can still be mutated
Check
Scan this JavaScript file for any use of var and flag every occurrence with line numbers.
Fix
Replace all var declarations with const or let as appropriate. Use const when the variable is never reassigned, let otherwise.
Explain
Explain why const and let are preferred over var, covering scope, hoisting, and temporal dead zone.
Code Review
Review scripts, client components, and browser execution paths related to Prefer const and let over var. Flag exact imports, event handlers, runtime side effects, or blocking operations that violate the rule, and state how the change should be verified in the browser.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/en/rules/javascript/const-let