ESLint — Complete Guide
ESLint — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of JavaScript Tutorial on Toolliyo Academy.
On this page
JavaScript Tutorial · Lesson 87 of 100
ESLint
Basics ✓ → Objects & data ✓ → Async & DOM ✓ → Advanced ✓ → Tools → Projects
Advanced · 5 — Testing & tools · ~10 min · JS Testing & Tooling
What is this?
ESLint finds problems and style issues in JavaScript — unused vars, missing await, questionable ==.
Why should you care?
Catches bugs before runtime and keeps team style consistent.
See it live — copy this example
Paste into an HTML file or the browser console (F12). Use Run below when the live editor is available.
// .eslintrc or eslint.config.js
// rules: { "no-unused-vars": "error", "eqeqeq": "warn" }Run Example »
Edit the code below and click Run to see the result in Toolliyo’s live editor.
What happened?
- Runs in editor and CI.
- Fix or disable rules with good reason only.
Practice next
- npm install -D eslint and npx eslint .
- Enable no-unused-vars and eqeqeq.
- Fix or justify disable comments sparingly.
- Add rule banishing console.log in src except warn/error.
- Run eslint --fix on a folder with formatting issues.
Remember
Static analysis Editor + CI Enforces consistency
ScriptVerse monorepo lint
Shared eslint-config-scriptverse enforces === and no floating promises across 12 packages.
Outcome: ESLint catches whole classes of bugs before code review.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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