.eslintrc.js

module.exports = {
  root: true,
  env: {
    node: true,
    es6: true,
    jest: true
  },
  parser: '@typescript-eslint/parser',
  parserOptions: {
    ecmaVersion: 2018,
    sourceType: 'module'
  },
  extends: ['eslint:recommended', 'plugin:prettier/recommended'],
  overrides: [
    {
      files: ['**/*.ts'],
      extends: [
        'eslint:recommended',
        'plugin:@typescript-eslint/eslint-recommended',
        'plugin:@typescript-eslint/recommended',
        'prettier/@typescript-eslint',
        'plugin:jest/recommended'
      ],
      plugins: ['@typescript-eslint', 'jest'],
      rules: {
        '@typescript-eslint/explicit-function-return-type': [
          'warn',
          {
            allowExpressions: true
          }
        ],
        '@typescript-eslint/no-unused-vars': 'warn',
        '@typescript-eslint/no-use-before-define': 'off',
        'no-console': 'error',
        // nededed for mixins to avoid unecessary warnings
        '@typescript-eslint/no-empty-interface': 'off'
      }
    }
  ]
}