Pluggable ESLint config for ECMAScript Next that you can import, extend and override

ESNext: Safety Checks and Best Practices with a bias toward code concision / brevity

Usage

In your js project directory:

npm install --save-dev eslint-config-esnext

And in your .eslintrc.yaml:

---
  extends:
    - esnext

Alternatively, in your .eslintrc.js or .eslintrc.json:

{
  "extends": ["esnext"]
}

To add a git-hook to your commits, consider using husky

npm install --save-dev husky

And in your package.json:

  "scripts": {
    "precommit": "eslint ."
  }

Config

This config is biased and opinionated, and errs on the side of too many rules instead of too few. Think of this as a superset of your repo's lint config, and discard what you don't like in it. It's easy to override and disable the rules you find inconvenient.

  env:
    es6: true
    commonjs: true

enables ES6 features and CommonJS modules

  parser: babel-eslint

enables parsing all babel supported code

  parserOptions:
    ecmaVersion: 7
    sourceType: module
    ecmaFeatures:
      impliedStrict: true
      modules: true
      experimentalObjectRestSpread: true

allows es2015 modules and es2016 object rest and spread to be parsed, and applies strict mode to all js code

  extends:
    - eslint:recommended
    - plugin:import/errors
    - plugin:import/warnings

includes the following rules:

• constructor-super: require super() calls in constructors

• no-case-declarations: disallow let, const, function and class declarations in case / default clauses inside switch blocks

• no-class-assign: disallow reassigning variables declared as classes

• no-cond-assign: disallow assignment operators in conditional expressions

• no-console: disallow the use of console

• no-const-assign: disallow reassigning const variables

• no-constant-condition: disallow constant expressions in conditions

• no-control-regex: disallow control characters in regular expressions

• no-debugger: disallow the use of debugger

• no-delete-var: disallow deleting variables

• no-dupe-args: disallow duplicate arguments in function definitions

• no-dupe-class-members: disallow duplicate class members

• no-dupe-keys: disallow duplicate keys in object literals

• no-duplicate-case: disallow duplicate case labels

• no-empty: disallow empty block statements

• no-empty-character-class: disallow empty character classes in regular expressions

• no-empty-pattern: disallow empty destructuring patterns

• no-ex-assign: disallow reassigning exceptions in catch clauses

• no-extra-boolean-cast: disallow unnecessary boolean casts

• no-extra-semi: disallow unnecessary semicolons

• no-fallthrough: disallow fallthrough of case statements

• no-func-assign: disallow reassigning function declarations

• no-inner-declarations: disallow function or var declarations in nested blocks

• no-invalid-regexp: disallow invalid regular expression strings in RegExp constructors

• no-irregular-whitespace: disallow irregular whitespace outside of strings and comments

• no-mixed-spaces-and-tabs: disallow mixed spaces and tabs for indentation

• no-new-symbol: disallow new operators with the Symbol object

• no-obj-calls: disallow calling global object properties as functions

• no-octal: disallow octal literals

• no-redeclare: disallow var redeclaration

• no-regex-spaces: disallow multiple spaces in regular expression literals

• no-self-assign: disallow assignments where both sides are exactly the same

• no-sparse-arrays: disallow sparse arrays

• no-this-before-super: disallow this/super before calling super() in constructors

• no-undef: disallow the use of undeclared variables unless mentioned in /-global -/ comments

• no-unexpected-multiline: disallow multiline expressions likely to cause ASI errors

• no-unreachable: disallow unreachable code after return, throw, continue, and break statements

• no-unsafe-finally: disallow control flow statements in finally blocks

• no-unused-labels: disallow unused labels

• no-unused-vars: disallow unused variables

• require-yield: require generator functions to contain yield

• use-isnan: disallow comparisons with NaN, requiring calls to isNaN() instead

• valid-typeof: enforce comparing typeof expressions against valid type strings

• import/no-unresolved: ensure imports point to a file/module that can be resolved

• import/named: ensure named imports correspond to a named export in the remote file

• import/namespace: ensure imported namespaces contain dereferenced properties as they are dereferenced

• import/default: ensure a default export is present, given a default import

• import/export: report any invalid exports, i.e. re-export of the same name

• import/no-named-as-default: report use of exported name as identifier of default export; set to warn only

• import/no-named-as-default-member: report use of exported name as property of default export; set to warn only

  rules:

selected from here, configured to:

• array-callback-return: enforce return statements in callbacks to array prototype methods such as map, reduce, find etc.
• arrow-body-style: require braces around arrow function bodies, as-needed
• class-methods-use-this: disallow class methods that don't use this
• dot-notation: enforce dot notation for accessing object properties whenever possible
• eqeqeq: prefer === and !== over == and !=
• import/no-amd: report AMD require and define calls
• import/no-commonjs: report CommonJS require calls and module.exports or exports.*
• import/no-duplicates: report repeated import of the same module in multiple places
• import/no-extraneous-dependencies: forbid the use of extraneous packages
• import/no-mutable-exports: forbid the use of mutable exports with var or let
• import/no-namespace: report namespace imports
• import/no-nodejs-modules: disallow node.js builtin modules
• import/prefer-default-export: prefer a default export if module exports a single name
• no-alert: disallow the use of alert, confirm, and prompt
• no-constant-condition: override eslint:recommended with checkLoops: false to avoid errors in infinite generators
• no-duplicate-imports: disallow duplicate module imports
• no-empty-function: disallow empty functions
• no-else-return: disallow else blocks after return statements in if blocks
• no-eval: disallow the use of eval()
• no-extend-native: disallow extending built-in or native objects
• no-extra-bind: disallow binding functions that don't use this
• no-global-assign: disallow assignments to native objects or read-only global variables
• no-implicit-globals: disallow var and named function declarations in the global scope, doesn't apply to modules
• no-implied-eval: disallow the use of eval()-like methods
• no-invalid-this: disallow this outside of constructors, classes or methods
• no-lonely-if: disallow if statements as the only statement in else blocks
• no-loop-func: disallow functions inside loops
• no-new: disallow new operators outside of assignments or comparisons
• no-new-func: disallow creating functions with the Function constructor
• no-new-wrappers: disallow creating objects with the String, Number, and Boolean constructors
• no-proto: disallow use of the __proto__ property
• no-script-url: disallow javascript: urls
• no-self-compare: disallow comparisons where both sides are exactly the same
• no-throw-literal: disallow throwing literals as exceptions
• no-unmodified-loop-condition: enforce updating the loop condition in each iteration
• no-unneeded-ternary: disallow ternary operators when simpler alternatives exist; defaultAssignment: false prefers || for default assignments
• no-unsafe-negation: disallow negating the left operand of relational operators like in and instanceof
• no-unused-expressions: disallow expressions that have no effect on the state of the program, with allowShortCircuit: true and allowTernary: true allowing &&, || and the ternary operator as shorthands for if and else
• no-use-before-define: disallow the use of variables before they are defined; nofunc ignores function declarations since they're hoisted
• no-useless-call: disallow unnecessary .call() and .apply()
• no-useless-computed-key: disallow unnecessary computed property keys in object literals
• no-useless-concat: disallow unnecessary concatenation of literals or template literals
• no-useless-constructor: disallow unnecessary constructors
• no-useless-escape: disallow unnecessary escape characters
• no-useless-rename: disallow renaming import, export, and destructured assignments to the same name
• no-var: require let or const instead of var
• no-with: disallow with statements
• object-shorthand: require method and property shorthand syntax for object literals
• operator-assignment: require assignment operator shorthand where possible
• prefer-arrow-callback: require callbacks to be arrow functions
• prefer-const: require const declarations for variables that are never reassigned after declared
• prefer-rest-params: require rest parameters instead of arguments
• prefer-spread: require spread operator instead of .apply()

ESNext Style Guide