ESLint

Tool for identifying and reporting on patterns found in ECMAScript/JavaScript code, with the goal of making code more consistent and avoiding bugs.

Install

npm init @eslint/config and then you can run npx eslint file.js.

eslint.config.js

module.exports = [
  {
    rules: {},
  },
];

.eslintrc.{js,yml,json} can also be used.

Every config file contains

• files - array of glob patterns indicating the files that the config object should apply to.
• ignores - array of glob patterns indicating the files that the config object should not apply to.
• languageOptions - configure javascript
  • ecmaVersion - default is ‘latest’
  • sourceType - default is ‘module’ for ‘js’ files
• plugins - name-value mapping of plugin names to plugin objects.
• rules - config rules.
• settings - name-value pairs that should be available to all rules.

rules

{
  "rules": {
    "semi": ["error", "always"]
  }
}

Error levels

• “off”
• “warn”
• “error”

extends

{
  "extends": "eslint:recommended"
}

All the rules from the eslint:recommended would be turned on.