.eslintrc.js

module.exports = {
  root: true,
  parser: 'babel-eslint',
  parserOptions: {
    ecmaVersion: 2018,
    sourceType: 'module',
    ecmaFeatures: {
      legacyDecorators: true
    }
  },
  plugins: [
    'ember'
  ],
  extends: [
    'eslint:recommended',
    'plugin:ember/recommended'
  ],
  env: {
    browser: true
  },
  rules: {
    'arrow-parens': ['error', 'always'],
    'arrow-spacing': ['error', { 'before': true, 'after': true }],
    'newline-after-var': 'off',
    'newline-before-return': 'off',
    'no-magic-numbers': ['off', { 'ignore': [-1, 0, 1] }],
    'object-curly-spacing': ['error', 'always'],
    'prefer-const': 'off',
    'prefer-rest-params': 'off',
    'space-before-blocks': ['error', 'always'],
    'space-before-function-paren': ['error', {
      anonymous: 'never',
      named: 'never',
      asyncArrow: 'always'
    }]
  },
  overrides: [
    // node files
    {
      files: [
        'ember-cli-build.js',
        'index.js',
        'testem.js',
        'blueprints/*/index.js',
        'config/**/*.js',
        'tests/dummy/config/**/*.js',
        'lib/**'
      ],
      excludedFiles: [
        'addon/**',
        'addon-test-support/**',
        'app/**',
        'tests/dummy/app/**',
      ],
      parserOptions: {
        sourceType: 'script',
        ecmaVersion: 2015
      },
      env: {
        browser: false,
        node: true
      },
      plugins: ['node'],
      rules: Object.assign({}, require('eslint-plugin-node').configs.recommended.rules, {
        // add your custom rules and overrides for node files here
      })
    },

    // test files
    {
      files: ['tests/**/*.js'],
      excludedFiles: ['tests/dummy/**/*.js'],
      env: {
        embertest: true
      }
    }
  ]
};