JavaScript Style Guide

eslint.json

{
  "env": {
    "es6": true
  },
  "rules": {
    "accessor-pairs": 2,
    "arrow-spacing": [2, {"before": true, "after": true}],
    "block-spacing": [2, "always"],
    "brace-style": [2, "1tbs", {"allowSingleLine": true}],
    "comma-dangle": [2, "always-multiline"],
    "comma-spacing": [2, {"before": false, "after": true}],
    "comma-style": [2, "last"],
    "constructor-super": 2,
    "curly": [2, "multi-line"],
    "dot-location": [2, "property"],
    "eol-last": 2,
    "func-call-spacing": [2, "never"],
    "indent": [2, 2, {"SwitchCase": 1, "MemberExpression": 1}],
    "key-spacing": [2, {"beforeColon": false, "afterColon": true}],
    "keyword-spacing": [2, {"before": true, "after": true}],
    "new-cap": [2, {"newIsCap": true, "capIsNew": false}],
    "new-parens": 2,
    "no-array-constructor": 2,
    "no-caller": 2,
    "no-class-assign": 2,
    "no-cond-assign": 2,
    "no-const-assign": 2,
    "no-constant-condition": [2, {"checkLoops": false}],
    "no-control-regex": 2,
    "no-debugger": 2,
    "no-delete-var": 2,
    "no-dupe-args": 2,
    "no-dupe-class-members": 2,
    "no-dupe-keys": 2,
    "no-duplicate-case": 2,
    "no-duplicate-imports": 2,
    "no-empty": 2,
    "no-empty-character-class": 2,
    "no-empty-pattern": 2,
    "no-eval": 2,
    "no-ex-assign": 2,
    "no-extend-native": 2,
    "no-extra-bind": 2,
    "no-extra-boolean-cast": 2,
    "no-extra-parens": [2, "functions"],
    "no-fallthrough": 2,
    "no-floating-decimal": 2,
    "no-func-assign": 2,
    "no-global-assign": 2,
    "no-implied-eval": 2,
    "no-inner-declarations": [2, "functions"],
    "no-invalid-regexp": 2,
    "no-irregular-whitespace": 2,
    "no-iterator": 2,
    "no-label-var": 2,
    "no-labels": [2, {"allowLoop": false, "allowSwitch": false}],
    "no-lone-blocks": 2,
    "no-mixed-spaces-and-tabs": 2,
    "no-multi-spaces": 2,
    "no-multi-str": 2,
    "no-multiple-empty-lines": [2, {"max": 1}],
    "no-native-reassign": 2,
    "no-negated-in-lhs": 2,
    "no-new": 2,
    "no-new-func": 2,
    "no-new-object": 2,
    "no-new-require": 2,
    "no-new-symbol": 2,
    "no-new-wrappers": 2,
    "no-obj-calls": 2,
    "no-octal": 2,
    "no-octal-escape": 2,
    "no-path-concat": 2,
    "no-proto": 2,
    "no-redeclare": 2,
    "no-regex-spaces": 2,
    "no-return-assign": [2, "except-parens"],
    "no-self-assign": 2,
    "no-self-compare": 2,
    "no-sequences": 2,
    "no-shadow-restricted-names": 2,
    "no-sparse-arrays": 2,
    "no-tabs": 2,
    "no-template-curly-in-string": 2,
    "no-this-before-super": 2,
    "no-throw-literal": 2,
    "no-trailing-spaces": 2,
    "no-undef": 2,
    "no-undef-init": 2,
    "no-unexpected-multiline": 2,
    "no-unmodified-loop-condition": 2,
    "no-unneeded-ternary": [2, {"defaultAssignment": false}],
    "no-unreachable": 2,
    "no-unsafe-finally": 2,
    "no-unsafe-negation": 2,
    "no-unused-vars": [2, {"vars": "all", "args": "none"}],
    "no-useless-call": 2,
    "no-useless-computed-key": 2,
    "no-useless-constructor": 2,    
    "no-useless-escape": 2,
    "no-useless-rename": 2,
    "no-var": 2,
    "no-whitespace-before-property": 2,
    "no-with": 2,
    "object-property-newline": [2, {"allowMultiplePropertiesPerLine": true}],
    "one-var": [2, {"initialized": "never"}],
    "operator-linebreak": [2, "after"],
    "padded-blocks": [2, "never"],
    "quote-props": [2, "as-needed"],
    "quotes": [2, "single", {"avoidEscape": true, "allowTemplateLiterals": true}],
    "rest-spread-spacing": [2, "never"],
    "semi": [2, "never"],
    "semi-spacing": [2, {"before": false, "after": true}],
    "space-before-blocks": [2, "always"],
    "space-before-function-paren": [2, {"anonymous": "always", "named": "never"}],
    "space-in-parens": [2, "never"],
    "space-infix-ops": 2,
    "space-unary-ops": [2, {"words": true, "nonwords": false}],
    "spaced-comment": [2, "always", {"line": {"markers": ["*package", "!", ","]}, "block": {"balanced": true, "markers": ["*package", "!", ","], "exceptions": ["*"]}}],
    "template-curly-spacing": [2, "never"],
    "unicode-bom": [2, "never"],
    "use-isnan": 2,
    "valid-typeof": 2,
    "wrap-iife": [2, "any"],
    "yield-star-spacing": [2, "both"],
    "yoda": [2, "never"]
  }
}

js-style.md

Kyle Hardgrave's JavaScript Style Guide

Just because

Not covered in this guide

All questions of style not covered in this guide should defer to the Airbnb JavaScript Style Guide.

Semicolons

Nope. They are unnecessary and ugly.

Lines beginning with a ( or [ should be avoided. They risk becoming function calls and array accesses in a semicolonless world. If they must be used (e.g., for an IIFE), they should be prefixed with a semicolon.

Line length and wrapping

Limit lines to 79 characters. This is still useful for editing multiple files on a 13-inch Macbook Pro.

Wrapped lines should be indented four spaces. E.g.:

if ((myVeryLongConditional1 && myVeryLongConditional2) ||
    myOtherPossibleConditional3) {
  //...
}

const result = myModule.myVeryLongFunctionCallName(longArgName1,
    longArgName2, longArgName3)

When wrapping lines with operators, the operator should fall at the end of the line. This includes boolean operator, ternary operators, and arithmetic operators, e.g., in string concatenation.

const myLongErrorMessage = 'Lines must end with an operator at the end.' +
    'Do not put the operator at the beginning!'
const myTernary = longConditionalQuestion ?
    module.doOneVerboselyNamedThing() :
    module.doAnotherVerboselyNamedThing()