Standard ESLint Setup for Svelte

.eslintrc.cjs

module.exports = {
  env: {
    browser: true,
    es2022: true
  },
  extends: [
    'standard',
    'eslint:recommended'
  ],
  parser: '@typescript-eslint/parser',
  parserOptions: {
    sourceType: 'module',
    ecmaVersion: 2022
  },
  plugins: [
    'svelte3',
    '@typescript-eslint'
  ],
  overrides: [
    {
      files: ['*.svelte'],
      processor: 'svelte3/svelte3'
    },
    {
      files: ['*.ts'],
      extends: [
        'plugin:@typescript-eslint/recommended',
        'plugin:@typescript-eslint/recommended-requiring-type-checking'
      ],
      parserOptions: {
        // Setting this inside the override is very important.
        project: ['./tsconfig.json']
      }
    },
    {
      files: ['*.js', '*.cjs', '*.mjs'],
      extends: [
        'plugin:@typescript-eslint/recommended'
      ]
    }
  ],
  rules: {
    // Needs fix from: https://github.com/sveltejs/eslint-plugin-svelte3/issues/41
    'no-multiple-empty-lines': ['error', { max: 1, maxBOF: 2, maxEOF: 0 }],
    'no-self-assign': 'warn',
    '@typescript-eslint/no-explicit-any': 'off'
  },
  settings: {
    'svelte3/typescript': () => require('typescript')
  }
}

package.json

{
  // ...
  "scripts": {
    // ...
    "check": "svelte-check --tsconfig ./tsconfig.json",
    "lint": "eslint './src/**/*.{js,ts,svelte}'",
    "lint:fix": "eslint --fix './src/**/*.{js,ts,svelte}'"
  }
  // ...
}

plugins.sh

# Install NPM packages.
npm install -D eslint-plugin-svelte3 eslint typescript @typescript-eslint/parser @typescript-eslint/eslint-plugin eslint-config-standard