.eslintrc.js

module.exports = {
  parser: '@typescript-eslint/parser',
  env: {
    browser: true,
    jest: true,
    es6: true,
    node: true,
  },
  extends: [
    'react-app',
    'plugin:react/recommended',
    'plugin:@typescript-eslint/recommended',
    'prettier',
  ],
  plugins: ['prettier'],
  rules: {
    'react/jsx-filename-extension': 'off',
    'jsx-a11y/click-events-have-key-events': 'off',
    // disable for all files - this means we can have plain JS files not causing errors
    '@typescript-eslint/explicit-function-return-type': 'off',
  },
  overrides: [
    {
      // and enable again specifically for TS files
      files: ['*.ts', '*.tsx'],
      rules: {
        '@typescript-eslint/explicit-function-return-type': [
          'error',
          {
            allowExpressions: true,
            allowTypedFunctionExpressions: true,
          },
        ],
      },
    },
  ],
  parserOptions: {
    ecmaFeatures: {
      jsx: true,
    },
    allowImportExportEverywhere: true,
    sourceType: 'module',
  },
  settings: {
    react: {
      version: 'detect', // Tells eslint-plugin-react to automatically detect the version of React to use
    },
  },
};