Resources

See links to the ESLint docs:

Rules

A reference for rules I typically like to know about or set, using my preferred values.

Each rule has its own allowed fields. Sometimes you set 2 or "error", or just 1.

Example:

{
  rules: {
    semi: [2, 'always'],
    semi: ['warn', 'always'],
    'no-console': 'error'
    'no-console': 2
  }
}

See Rules in the docs. It provides descriptions and link to the rule’s page.

See below rule names and some recommended values (not all values).

Name Values Link
semi [2, "always"]  
comma-dangle 'always-multiline'. Using always is to aggressive like import { x, y, } from "bar". docs
quotes [2, "single"] or [2, "double"] docs
no-console 'off' docs
no-console 1  
no-undef 1  
indent ["error", 2] - you’ll get 4 spaces for just "error" docs

Script settings

Approaches to ignore within a script, where [RULE, ] below could be empty, or one more or more rules such as no-alert, quotes, semi.

Minimal setting would be to use double quotes and semi-colons, or flip it to single quotes and no semi-colons.

You can also use an IDE formatter or the CLI (eslint . --fix) to change files based on your config or default settings.

For more detail than below, you can set level as 0, 1 or 2 - Configuring rules.

Ignore entire file

Place at the top of the file:

/* eslint-disable [RULE, ] */
COMMAND
COMMAND

Ignore a section

COMMAND

/* eslint-disable [RULE, ] */
COMMAND
COMMAND
/* eslint-enable [RULE, ] */

COMMAND

Ignore next line

// eslint-disable-next-line [RULE, ]
COMMAND

Ignore current line

COMMAND // eslint-disable-line [RULE, ]

Config files

See the ESLint section of my Code Cookbook for entire configs you can copy and paste.

The ESLint config

From Configuration file format in the docs.

  1. .eslintrc.js
  2. .eslintrc.yaml or .eslintrc.yml
  3. .eslintrc.json
  4. .eslintrc - DEPRECATED, as it can be JSON or YAML
  5. package.json - eslintConfig field.

ESLint ignore config

See Ignoring Files and Directories in the docs.

This is a plain text file with glob patterns.

Samples from the docs:

  • .eslintignore 
      **/*.js
  • .eslintignore 
      # Ignore files compiled from TypeScript and CoffeeScript
  **/*.{ts,coffee}.js
  • .eslintignore 
      # Ignore built files except build/index.js
  build/
  !build/index.js

Note that node_modules is ignored by default.

Logging ignored paths

When you pass directories to ESLint, files and directories are silently ignored.

If you pass a specific file to ESLint, then you will see a warning indicating that the file was skipped.

Example file:

foo.js

When running:

$ eslint foo.js

The output message will tell your foo.js was ignored and that you can use the --no-ignore flag.