.eslintrc.js

module.exports = {
  "env": {
    "browser": true,
    "es6": true,
    "node": true,
  },
  "settings": {
    "import/resolver": "webpack",
  },
  "extends": [
    "eslint:recommended",
    "plugin:import/errors",
    "plugin:import/warnings",
  ],
  "parserOptions": {
    "sourceType": "module",
    "ecmaVersion": 2018,
  },
  "rules": {
    // Basic settings
    "indent": ["warn", 4],                // Indent with 4 spaces
    "no-tabs": ["warn"],                   // Don't use tabs
    "no-trailing-spaces": ["warn"],                   // Don't allow trailing spaces
    "linebreak-style": ["error", "unix"],          // End lines with UNIX line breaks
    "max-len": ["warn", { "code": 120 }],  // Line length is limited by 120 characters
    "semi": ["error", "never"],         // Don't use semicolons if not necessary
    "semi-style": ["error", "first"],         // If necessary, write semicolon at the beginning of the line
    "eol-last": ["error", "always"],        // enforces at least one newline (or absence thereof) at the end of non-empty files

    // Code settings
    "no-use-before-define": ["error"],                  // Define functions, classes and variables before you use them
    "no-var": ["warn"],                   // Don't allow var
    "prefer-const": ["warn", { "ignoreReadBeforeAssign": true }],  // If let is not assigned to, prefer const
    "no-return-assign": ["error", "always"],        // Don't allow assingment in return statement
    "eqeqeq": ["error", "smart"],         // Reqire use of === and !== instead of == and != (with a few exceptions)
    "complexity": ["warn", 10],               // Maximum cyclomatic complexity
    "sort-imports": ["error", {
      "allowSeparatedGroups": true,                   // Allow newlines between import groups
      "ignoreDeclarationSort": true,                  // Ignore order of declarations, but still sort members of each import
    }],
    "import/order": ["error", {
      "alphabetize": { "order": "asc" },                // Sort imports alphabetically by module
      "newlines-between": "always",                   // Enforce newlines between import groups
      "groups": ["builtin", "external", "internal", "parent", "sibling", "index"],
      "pathGroups": [{
        "pattern": "ferda/**",
        "group": "internal",
      }, {
        "pattern": "ferda/../**",
        "group": "internal",
      }],
      "pathGroupsExcludedImportTypes": ["builtin"],
    }],

    // Spacing settings
    "space-before-blocks": ["warn"],                   // Require at least one preceding space before blocks
    "keyword-spacing": ["warn"],                   // Reqiure spacing around keywords
    "func-call-spacing": ["error", "never"],         // Don't allow spaces between function call and arguments
    "space-before-function-paren": ["error", "never"],  // Don't allow spaces before function definition parenthesis
    "spaced-comment": ["warn", "always"],         // Require whitespace after //
    "space-in-parens": ["warn", "never"],          // Don't allow spaces in parenthesis
    "comma-spacing": ["warn"],                   // Reqire space after comma, don't allow space before
    "space-infix-ops": ["warn"],                   // Require spaces around infix operators (including =)
    "quotes": ["warn", "single", { "avoidEscape": true, "allowTemplateLiterals": true }], // Requires the use of single quotes, allows strings to use single-quotes or double-quotes so long as the string contains a quote that would have to be escaped otherwise, allows strings to use backticks
    "comma-dangle": ["warn", "always-multiline"],  // Require for the last item in multiline object to be followed by comma
    "no-multiple-empty-lines": ["warn", { "max": 1, "maxEOF": 0, "maxBOF": 0, }], // Allow max one empty line
  }
};