Possible Errors

Best Practices

accessor-pairs

Turn on
Enforce getter and setter pairs in objects

array-callback-return

Turn on
Enforce return statements in callbacks of array methods

block-scoped-var

Turn on
Enforce the use of variables within the scope they are defined

class-methods-use-this

Turn on
Enforce that class methods utilize this

complexity

Turn on
Enforce a maximum cyclomatic complexity allowed in a program

consistent-return

Turn on
Require return statements to either always or never specify values

curly

Fixable
Turn on
Enforce consistent brace style for all control statements

default-case

Turn on
Require default cases in switch statements

dot-location

Fixable
Turn on
Enforce consistent newlines before and after dots

dot-notation

Fixable
Turn on
Enforce dot notation whenever possible

eqeqeq

Fixable
Turn on
Require the use of === and !==

guard-for-in

Turn on
Require for-in loops to include an if statement

max-classes-per-file

Turn on
Enforce a maximum number of classes per file

no-alert

Turn on
Disallow the use of alert, confirm, and prompt

no-caller

Turn on
Disallow the use of arguments.caller or arguments.callee

no-case-declarations

Recommended
Turn on
Disallow lexical declarations in case clauses

no-div-regex

Turn on
Disallow division operators explicitly at the beginning of regular expressions

no-else-return

Fixable
Turn on
Disallow else blocks after return statements in if statements

no-empty-function

Turn on
Disallow empty functions

no-empty-pattern

Recommended
Turn on
Disallow empty destructuring patterns

no-eq-null

Turn on
Disallow null comparisons without type-checking operators

no-eval

Turn on
Disallow the use of eval()

no-extend-native

Turn on
Disallow extending native types

no-extra-bind

Fixable
Turn on
Disallow unnecessary calls to .bind()

no-extra-label

Fixable
Turn on
Disallow unnecessary labels

no-fallthrough

Recommended
Turn on
Disallow fallthrough of case statements

no-floating-decimal

Fixable
Turn on
Disallow leading or trailing decimal points in numeric literals

no-global-assign

Recommended
Turn on
Disallow assignments to native objects or read-only global variables

no-implicit-coercion

Fixable
Turn on
Disallow shorthand type conversions

no-implicit-globals

Turn on
Disallow variable and function declarations in the global scope

no-implied-eval

Turn on
Disallow the use of eval()-like methods

no-invalid-this

Turn on
Disallow this keywords outside of classes or class-like objects

no-iterator

Turn on
Disallow the use of the __iterator__ property

no-labels

Turn on
Disallow labeled statements

no-lone-blocks

Turn on
Disallow unnecessary nested blocks

no-loop-func

Turn on
Disallow function declarations and expressions inside loop statements

no-magic-numbers

Turn on
Disallow magic numbers

no-multi-spaces

Fixable
Turn on
Disallow multiple spaces

no-multi-str

Turn on
Disallow multiline strings

no-new

Turn on
Disallow new operators outside of assignments or comparisons

no-new-func

Turn on
Disallow new operators with the Function object

no-new-wrappers

Turn on
Disallow new operators with the String, Number, and Boolean objects

no-octal

Recommended
Turn on
Disallow octal literals

no-octal-escape

Turn on
Disallow octal escape sequences in string literals

no-param-reassign

Turn on
Disallow reassigning function parameters

no-proto

Turn on
Disallow the use of the __proto__ property

no-redeclare

Recommended
Turn on
Disallow variable redeclaration

no-restricted-properties

Turn on
Disallow certain properties on certain objects

no-return-await

Turn on
Disallow unnecessary return await

no-script-url

Turn on
Disallow javascript: urls

no-return-assign

Turn on
Disallow assignment operators in return statements

no-self-assign

Recommended
Turn on
Disallow assignments where both sides are exactly the same

no-self-compare

Turn on
Disallow comparisons where both sides are exactly the same

no-sequences

Turn on
Disallow comma operators

no-throw-literal

Turn on
Disallow throwing literals as exceptions

no-unmodified-loop-condition

Turn on
Disallow unmodified loop conditions

no-unused-labels

Recommended
Fixable
Turn on
Disallow unused labels

no-unused-expressions

Turn on
Disallow unused expressions

no-useless-call

Turn on
Disallow unnecessary calls to .call() and .apply()

no-useless-catch

Turn on
Disallow unnecessary catch clauses

no-useless-concat

Turn on
Disallow unnecessary concatenation of literals or template literals

no-useless-escape

Recommended
Turn on
Disallow unnecessary escape characters

no-useless-return

Fixable
Turn on
Disallow redundant return statements

no-void

Turn on
Disallow void operators

no-warning-comments

Turn on
Disallow specified warning terms in comments

no-with

Turn on
Disallow with statements

prefer-promise-reject-errors

Turn on
Require using Error objects as Promise rejection reasons

radix

Turn on
Enforce the consistent use of the radix argument when using parseInt()

require-await

Turn on
Disallow async functions which have no await expression

require-unicode-regexp

Turn on
Enforce the use of u flag on RegExp

vars-on-top

Turn on
Require var declarations be placed at the top of their containing scope

wrap-iife

Fixable
Turn on
Require parentheses around immediate function invocations

yoda

Fixable
Turn on
Require or disallow “Yoda” conditions

Strict Mode

Variables

Node.js and CommonJS

Stylistic Issues

ECMAScript 6

DownloadPreview

guard-for-in

- Require for-in loops to include an if statement

This rule is aimed at preventing unexpected behavior that could arise from using a for in loop without filtering the results in the loop. As such, it will warn when for in loops do not filter their results with an if statement.

What ESLint should do when it catches the rule break

Show a warning

Rule examples

You can check them out here.

eqeqeqmax-classes-per-file