eslint
ESLint is the #1 JavaScript linter by downloads on npm (over 77M weekly downloads) and the most widely adopted pluggable linting utility for JavaScript and JSX. It helps you find and fix problems with your JavaScript code through static analysis.
Key features:
- Static Code Analysis: Quickly finds problems in JavaScript code without executing it
- Automatic Fixing: Many problems can be automatically fixed with syntax-aware corrections
- Highly Configurable: Completely customizable rules, parsers, and plugins ecosystem
- Built-in Editor Integration: Works seamlessly with most text editors
- Extensible Plugin System: Thousands of community plugins for frameworks like React, Vue, Node.js
- Multiple Output Formats: Supports various output formats including SARIF for security tools
- Custom Rules: Write your own rules that work alongside ESLint's built-in rules
Common code quality checks:
- Syntax Errors: Catches JavaScript syntax issues and typos
- Code Style: Enforces consistent formatting, naming conventions, and code structure
- Best Practices: Identifies problematic patterns and suggests improvements
- Security Issues: Detects potential security vulnerabilities (with security plugins)
- Performance: Identifies performance anti-patterns and optimizations
Popular configurations:
- Airbnb Style Guide: Industry-standard JavaScript style guide
- Standard: Minimal, opinionated code style with no configuration
- Prettier Integration: Seamless integration with Prettier for code formatting
ESLint requires a custom configuration file applicable to your project. You can create it by typing npx eslint --init
in the root of your repository.
Used by companies like Microsoft, Airbnb, Netflix, and Facebook, ESLint helps maintain code quality and consistency across JavaScript projects of all sizes.
eslint documentation
- Version in MegaLinter: 8.57.1
- Visit Official Web Site
- See How to configure eslint rules
- See How to disable eslint rules in files
- See How to ignore files and directories with eslint
- You can define a
.eslintignore
file to ignore files and folders
- You can define a
- See Index of problems detected by eslint
Configuration in MegaLinter
- Enable eslint by adding
JAVASCRIPT_ES
in ENABLE_LINTERS variable - Disable eslint by adding
JAVASCRIPT_ES
in DISABLE_LINTERS variable
- Enable autofixes by adding
JAVASCRIPT_ES
in APPLY_FIXES variable
Variable | Description | Default value |
---|---|---|
JAVASCRIPT_ES_ARGUMENTS | User custom arguments to add in linter CLI call Ex: -s --foo "bar" |
|
JAVASCRIPT_ES_COMMAND_REMOVE_ARGUMENTS | User custom arguments to remove from command line before calling the linter Ex: -s --foo "bar" |
|
JAVASCRIPT_ES_FILTER_REGEX_INCLUDE | Custom regex including filter Ex: (src\|lib) |
Include every file |
JAVASCRIPT_ES_FILTER_REGEX_EXCLUDE | Custom regex excluding filter Ex: (test\|examples) |
Exclude no file |
JAVASCRIPT_ES_CLI_LINT_MODE | Override default CLI lint mode - file : Calls the linter for each file- list_of_files : Call the linter with the list of files as argument- project : Call the linter from the root of the project |
list_of_files |
JAVASCRIPT_ES_FILE_EXTENSIONS | Allowed file extensions. "*" matches any extension, "" matches empty extension. Empty list excludes all filesEx: [".py", ""] |
[".js", ".vue"] |
JAVASCRIPT_ES_FILE_NAMES_REGEX | File name regex filters. Regular expression list for filtering files by their base names using regex full match. Empty list includes all files Ex: ["Dockerfile(-.+)?", "Jenkinsfile"] |
Include every file |
JAVASCRIPT_ES_PRE_COMMANDS | List of bash commands to run before the linter | None |
JAVASCRIPT_ES_POST_COMMANDS | List of bash commands to run after the linter | None |
JAVASCRIPT_ES_UNSECURED_ENV_VARIABLES | List of env variables explicitly not filtered before calling JAVASCRIPT_ES and its pre/post commands | None |
JAVASCRIPT_ES_CONFIG_FILE | eslint configuration file nameUse LINTER_DEFAULT to let the linter find it |
.eslintrc.json |
JAVASCRIPT_ES_RULES_PATH | Path where to find linter configuration file | Workspace folder, then MegaLinter default rules |
JAVASCRIPT_ES_DISABLE_ERRORS | Run linter but consider errors as warnings | false |
JAVASCRIPT_ES_DISABLE_ERRORS_IF_LESS_THAN | Maximum number of errors allowed | 0 |
JAVASCRIPT_ES_CLI_EXECUTABLE | Override CLI executable | ['eslint'] |
IDE Integration
Use eslint in your favorite IDE to catch errors before MegaLinter !
MegaLinter Flavors
This linter is available in the following flavors
Flavor | Description | Embedded linters | Info | |
---|---|---|---|---|
![]() |
all | Default MegaLinter Flavor | 127 | |
cupcake | MegaLinter for the most commonly used languages | 88 | ||
dotnetweb | Optimized for C, C++, C# or VB based projects with JS/TS | 74 | ||
javascript | Optimized for JAVASCRIPT or TYPESCRIPT based projects | 60 |
Behind the scenes
How are identified applicable files
- Activated only if one of these files is found:
.eslintrc.json, .eslintrc.yml, .eslintrc.yaml, .eslintrc.js, .eslintrc.cjs, package.json:eslintConfig
- File extensions:
.js
,.vue
How the linting is performed
- eslint is called once with the list of files as arguments (
list_of_files
CLI lint mode)
Example calls
eslint myfile.js
eslint -c .eslintrc.json --no-eslintrc --no-ignore myfile.js
eslint --fix -c .eslintrc.json --no-eslintrc --no-ignore myfile.js
Help content
eslint [options] file.js [file.js] [dir]
Basic configuration:
--no-eslintrc Disable use of configuration from .eslintrc.*
-c, --config path::String Use this configuration, overriding .eslintrc.* config options if present
--env [String] Specify environments
--ext [String] Specify JavaScript file extensions
--global [String] Define global variables
--parser String Specify the parser to be used
--parser-options Object Specify parser options
--resolve-plugins-relative-to path::String A folder where plugins should be resolved from, CWD by default
Specify Rules and Plugins:
--plugin [String] Specify plugins
--rule Object Specify rules
--rulesdir [path::String] Load additional rules from this directory. Deprecated: Use rules from plugins
Fix Problems:
--fix Automatically fix problems
--fix-dry-run Automatically fix problems without saving the changes to the file system
--fix-type Array Specify the types of fixes to apply (directive, problem, suggestion, layout)
Ignore Files:
--ignore-path path::String Specify path of ignore file
--no-ignore Disable use of ignore files and patterns
--ignore-pattern [String] Pattern of files to ignore (in addition to those in .eslintignore)
Use stdin:
--stdin Lint code provided on <STDIN> - default: false
--stdin-filename String Specify filename to process STDIN as
Handle Warnings:
--quiet Report errors only - default: false
--max-warnings Int Number of warnings to trigger nonzero exit code - default: -1
Output:
-o, --output-file path::String Specify file to write report to
-f, --format String Use a specific output format - default: stylish
--color, --no-color Force enabling/disabling of color
Inline configuration comments:
--no-inline-config Prevent comments from changing config or rules
--report-unused-disable-directives Adds reported errors for unused eslint-disable and eslint-enable directives
--report-unused-disable-directives-severity String Chooses severity level for reporting unused eslint-disable and eslint-enable directives - either: off, warn, error, 0, 1, or 2
Caching:
--cache Only check changed files - default: false
--cache-file path::String Path to the cache file. Deprecated: use --cache-location - default: .eslintcache
--cache-location path::String Path to the cache file or directory
--cache-strategy String Strategy to use for detecting changed files in the cache - either: metadata or content - default: metadata
Miscellaneous:
--init Run config initialization wizard - default: false
--env-info Output execution environment information - default: false
--no-error-on-unmatched-pattern Prevent errors when pattern is unmatched
--exit-on-fatal-error Exit with exit code 2 in case of fatal error - default: false
--debug Output debugging information
-h, --help Show help
-v, --version Output the version number
--print-config path::String Print the configuration for the given file
Installation on mega-linter Docker image
- Dockerfile commands :
# renovate: datasource=npm depName=eslint
ARG NPM_ESLINT_VERSION=8.57.1
# renovate: datasource=npm depName=eslint-config-airbnb
ARG NPM_ESLINT_CONFIG_AIRBNB_VERSION=19.0.4
# renovate: datasource=npm depName=eslint-config-prettier
ARG NPM_ESLINT_CONFIG_PRETTIER_VERSION=10.1.5
# renovate: datasource=npm depName=eslint-config-standard
ARG NPM_ESLINT_CONFIG_STANDARD_VERSION=17.1.0
# renovate: datasource=npm depName=eslint-plugin-import
ARG NPM_ESLINT_PLUGIN_IMPORT_VERSION=2.32.0
# renovate: datasource=npm depName=eslint-plugin-jest
ARG NPM_ESLINT_PLUGIN_JEST_VERSION=29.0.1
# renovate: datasource=npm depName=eslint-plugin-n
ARG NPM_ESLINT_PLUGIN_N_VERSION=16.6.2
# renovate: datasource=npm depName=eslint-plugin-prettier
ARG NPM_ESLINT_PLUGIN_PRETTIER_VERSION=5.5.1
# renovate: datasource=npm depName=eslint-plugin-promise
ARG NPM_ESLINT_PLUGIN_PROMISE_VERSION=6.6.0
# renovate: datasource=npm depName=eslint-plugin-vue
ARG NPM_ESLINT_PLUGIN_VUE_VERSION=10.3.0
# renovate: datasource=npm depName=@babel/core
ARG NPM_BABEL_CORE_VERSION=7.28.0
# renovate: datasource=npm depName=@babel/eslint-parser
ARG NPM_BABEL_ESLINT_PARSER_VERSION=7.28.0
# renovate: datasource=npm depName=@microsoft/eslint-formatter-sarif
ARG NPM_MICROSOFT_ESLINT_FORMATTER_SARIF_VERSION=3.1.0
- NPM packages (node.js):
- eslint@8.57.1
- eslint-config-airbnb@19.0.4
- eslint-config-prettier@10.1.5
- eslint-config-standard@17.1.0
- eslint-plugin-import@2.32.0
- eslint-plugin-jest@29.0.1
- eslint-plugin-n@16.6.2
- eslint-plugin-prettier@5.5.1
- eslint-plugin-promise@6.6.0
- eslint-plugin-vue@10.3.0
- @babel/core@7.28.0
- @babel/eslint-parser@7.28.0
- @microsoft/eslint-formatter-sarif@3.1.0