CheatESLint JavaScript linter
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Start here
npm init @eslint/config@latest
Create a config
npx eslint .Lint the project
npx eslint --fix .
Auto-fix problems
npx eslint <file>
Lint one file
npx eslint --quiet .
Errors only
npx eslint --max-warnings 0 .
Fail on warnings
npx eslint --cache .
Skip unchanged files
npx eslint --print-config <file>
Show effective config
Concepts
- Files globs from CLI
- Flat config eslint.config.js
- Problems error / warn
- Report -f, exit code
Running
npx eslint .Lint the current directory
npx eslint <file> <dir>
Lint specific files or folders
npx eslint "src/**/*.{js,ts}"
Lint a quoted glob
Quote globs so ESLint expands them, not the shell.
npx eslint --stdin --stdin-filename <path>
Lint code from stdin
npx eslint --ignore-pattern <glob> .
Skip files for this run
npx eslint --no-warn-ignored <file>
Silence the warning for ignored files
Useful when a pre-commit hook passes ignored files.
npx eslint --no-error-on-unmatched-pattern
<glob>
Do not fail when a glob matches nothing
npx eslint --concurrency auto .
Lint in parallel worker threads
Fixing
npx eslint --fix .
Apply automatic fixes
npx eslint --fix --fix-type suggestion,layout .
Only apply some fix kinds
Types: problem, suggestion, layout, directive.
npx eslint --cache --fix .
Fix and remember what is clean
Warnings and exit codes
npx eslint --quiet .
Hide warnings, show errors
npx eslint --max-warnings 0 .
Exit 1 if any warning appears
echo $?
0 clean, 1 lint failure, 2 config or crash
npx eslint --rule '<rule>: error' .
Set a rule for this run only
Quote the value; the syntax is rule-name: severity or JSON.
npx eslint --report-unused-disable-directives .
Flag useless disable comments
Output
npx eslint -f json .
Machine-readable JSON
npx eslint -f <name> .
Pick a formatter
Built in: stylish (default), json, json-with-metadata, html.
npx eslint -f json -o <file> .
Write the report to a file
Cache and speed
npx eslint --cache .
Only lint changed files
npx eslint --cache --cache-strategy content .
Detect changes by content, not mtime
Handy in CI where checkouts reset modification times.
Config
npm init @eslint/config@latest
Create eslint.config.js interactively
npx eslint -c <file> .
Use a specific config file
npx eslint --print-config <file>
Show the config a file gets
npx eslint --debug <file>
Print debug output
import js from "@eslint/js";import globals from "globals";export default [ { ignores: ["dist/", "coverage/"] }, js.configs.recommended, { files: ["**/*.js"], languageOptions: { globals: globals.node }, rules: { "no-unused-vars": "warn", eqeqeq: "error" }, },];import { defineConfig } from "eslint/config";import js from "@eslint/js";export default defineConfig([ { files: ["src/**/*.js"], plugins: { js }, extends: ["js/recommended"] }, { files: ["test/**"], rules: { "no-console": "off" } },]);{ ignores: ["dist/"] }
Global ignore (only key in the object)
With other keys it only ignores for that one config object.
{ files: ["**/*.ts"], ... }
Limit a config object to matching files
Inline comments
// eslint-disable-next-line <rule>
Silence a rule on the next line
// eslint-disable-line <rule>
Silence a rule on this line
/* eslint-disable <rule> */
Disable from here to the end of file
// eslint-disable-next-line <rule> --
<reason>
Document why after --
Recipes
npx eslint --max-warnings 0 --cache --cache-strategy content .git diff --name-only --cached --diff-filter=d -- '*.js' \ | xargs npx eslint --max-warnings 0npx eslint --suppress-all .# fix gradually, then drop stale entriesnpx eslint --prune-suppressions
