eslint-config-esnext

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

Usage

In your js project directory:

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

And in your .eslintrc.yaml:

---
  extends:
    - esnext
    - esnext/style-guide #optional

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

{
  "extends": ["esnext", "esnext/style-guide"]
}

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

npm install --save-dev husky

And in your package.json:

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

---

safety checks and best practices supporting commonly used ESNext features with a bias toward code concision / brevity

  env:
    es6: true

enables es6 features

  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

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-native-reassign: disallow assignments to native objects or read-only global variables
• no-negated-in-lhs: disallow negating the left operand in in expressions
• 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

  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
• dot-notation: enforce dot notation for accessing object properties whenever possible
• eqeqeq: prefer === and !== over == and !=
• 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-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-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-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-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-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()

---

style-guide: for consistency, readability and more brevity

---
  plugins:
    - babel

provides some alternatives to standard rules that are better compatible with babel-supported code

  rules:

selected from here, configured to:

• array-bracket-spacing: enforce spacing inside array brackets
• arrow-parens: require parentheses around arrow function arguments, as-needed
• arrow-spacing: enforce spacing before and after => in arrow functions
• babel/generator-star-spacing: alternative to generator-star-spacing that handles async functions and await properly
• block-spacing: enforce spacing inside single-line blocks
• brace-style: enforce K&R brace style
• camelcase: enforce camelcase naming convention, ignore object properties
• comma-spacing: disallow spacing before and enforce after commas
• comma-style: allow commas only after and on the same line as an array element, object property, or variable declaration
• computed-property-spacing: disallow spaces inside computed property brackets
• consistent-this: allow this to only be assigned to a variable named that
• curly: require curly braces around blocks if they contain multiple statements, disallow braces if not
• dot-location: require the dot in a member expression to be on the same line as the property portion
• generator-star-spacing: enforce spacing before and disallow after * operators in generator functions
• indent: enforce tabs (why?), SwitchCase: 1; override in your .eslintrc if you disagree
• key-spacing: disallow spacing after keys and enforce spacing before values in object literal properties
• keyword-spacing: enforce spacing before and after keywords
• linebreak-style: enforce unix linebreaks
• newline-per-chained-call: require a newline after each call in a method chain exceeding 2 calls
• no-extra-parens: disallow unnecessary parentheses; set to warn only
• no-multi-spaces: disallow multiple spaces that are not used for indentation
• no-spaced-func: disallow spacing between function identifiers and their applications
• no-trailing-spaces: disallow trailing whitespace at the end of lines
• no-whitespace-before-property: disallow whitespace before properties
• object-curly-newline: require line breaks inside braces if there are line breaks inside properties or between properties in object literals
• object-curly-spacing: enforce spacing inside curly braces
• object-property-newline: enforce placing object properties on separate lines; set to warn only
• one-var-declaration-per-line: require newlines around var initializations
• operator-linebreak: require the line break to be placed before the operator
• quote-props: disallow unneeded quotes around object literal property names
• quotes: enforce single quotes, while allowing template literals and double quotes to avoid escape characters
• rest-spread-spacing: disallow spacing between rest and spread operators and their expressions
• semi: disallow semicolons (why?); override in your .eslintrc if you disagree
• semi-spacing: disallow spacing before and enforce after semicolons
• sort-imports: enforce sorted import declarations within modules
• space-before-blocks: enforce spacing before blocks
• space-before-function-paren: enforce spacing before function definition opening parenthesis
• space-in-parens: disallow spacing inside parentheses
• space-infix-ops: require spacing around operators
• space-unary-ops: require spacing between operand and unary word operators, disallow it between operand and unary non-word operator
• spaced-comment: enforce spacing after the // or /* in a comment
• template-curly-spacing: require spacing around embedded expressions of template strings
• valid-jsdoc: enforce valid JSDoc comments; set to warn only