.eslintrc.js

module.exports = {
  "env": {
    "es6": true,
    "browser": true,
    "commonjs": true
  },

  "parserOptions": {
    "sourceType": "module",
    "ecmaVersion": 2017
  },

  "extends": [
    "eslint:recommended"
  ],

  "rules": {
    // basics
    "indent": [ "error", 2, { // indentation should be 2 spaces
      "flatTernaryExpressions": true, // ternary should be performed in flat
      "MemberExpression": 0 // member chain should be performed in flat
    } ], // it forces 2 spaces indentation
    "linebreak-style": [ "error", "unix" ], // fuck you, CRLF
    "quotes": [ "error", "single" ], // quotes must be single
    "eqeqeq": [ "error", "always" ], // fuck you, `==`

    // variables
    "no-unused-vars": [ "off" ], // unused vars are okay
    "no-undef": [ "warn" ], // draws yellow line below undefined vars

    // omittables
    "semi": [ "error", "always" ], // semicolon is required
    "curly": [ "error" ], // it kills `if (foo) bar++;`
    "arrow-parens": [ "error", "always" ], // it kills `arg => { func(); }`

    // force spacing (I prefer super sparse code!)
    "array-bracket-spacing": [ "error", "always" ], // it kills `[val1, val2]`
    "arrow-spacing": [ "error", { "before": true, "after": true } ], // it kills `( arg )=>{ func(); }`
    "block-spacing": [ "error", "always" ], // it kills `if ( cond ) {func();}`
    "comma-spacing": [ "error", { "before": false, "after": true } ], // it kills `func( arg1,arg2 )`
    "computed-property-spacing": [ "error", "always" ], // it kills `arr[i]`
    "key-spacing": [ "error", { "beforeColon": false, "afterColon": true } ], // it kills `{ key:val }`
    "keyword-spacing": [ "error", { "before": true, "after": true } ], // it kills `}else{`
    "object-curly-spacing": [ "error", "always" ], // it kills `{key: val}`
    "semi-spacing": [ "error", { "before": false, "after": true } ], // it kills `func1();func2();`
    "space-before-blocks": [ "error", "always" ], // it kills `if (cond){`
    "space-in-parens": [ "error", "always" ], // it kills `func (arg)`
    "space-infix-ops": [ "error" ], // it kills val1+val2
    "space-unary-ops": [ "error", { "words": true, "nonwords": false, "overrides": { "++": true, "--": true } } ], // it kills `val++`
    "spaced-comment": [ "error", "always" ], // it kills `//this is comment`

    // ban spacing
    "func-call-spacing": [ "error", "never" ], // no-trailing-spaces. yea.
    "no-trailing-spaces": [ "error", { "ignoreComments": true } ], // no-trailing-spaces. yea.
    "no-whitespace-before-property": [ "error" ], // it kills `obj .key`
    "space-before-function-paren": [ "error", { "anonymous": "never", "named": "never", "asyncArrow": "always" } ], // it kills `func()`

    // others
    "no-eval": [ "warn" ], // wow, are you really going to use `eval()`? are you mad lol
    "no-implied-eval": [ "warn" ], // ok don't
    'no-console': process.env.NODE_ENV === 'production' ? 'error' : 'off', // here is nodejs, console.log is innocent
    'no-debugger': process.env.NODE_ENV === 'production' ? 'error' : 'off' // debuggerとか使う？
  }
};