Possible Errors

Best Practices

accessor-pairs

Enforce getter and setter pairs in objects

array-callback-return

Enforce return statements in callbacks of array methods

block-scoped-var

Enforce the use of variables within the scope they are defined

class-methods-use-this

Enforce that class methods utilize this

complexity

Enforce a maximum cyclomatic complexity allowed in a program

consistent-return

Require return statements to either always or never specify values

curly

Enforce consistent brace style for all control statements

default-case

Require default cases in switch statements

dot-location

Enforce consistent newlines before and after dots

dot-notation

Enforce dot notation whenever possible

eqeqeq

Require the use of === and !==

guard-for-in

Require for-in loops to include an if statement

max-classes-per-file

Enforce a maximum number of classes per file

no-alert

Disallow the use of alert, confirm, and prompt

no-caller

Disallow the use of arguments.caller or arguments.callee

no-case-declarations

Disallow lexical declarations in case clauses

no-div-regex

Disallow division operators explicitly at the beginning of regular expressions

no-else-return

Disallow else blocks after return statements in if statements

no-empty-function

Disallow empty functions

no-empty-pattern

Disallow empty destructuring patterns

no-eq-null

Disallow null comparisons without type-checking operators

no-eval

Disallow the use of eval()

no-extend-native

Disallow extending native types

no-extra-bind

Disallow unnecessary calls to .bind()

no-extra-label

Disallow unnecessary labels

no-fallthrough

Disallow fallthrough of case statements

no-floating-decimal

Disallow leading or trailing decimal points in numeric literals

no-global-assign

Disallow assignments to native objects or read-only global variables

no-implicit-coercion

Disallow shorthand type conversions

no-implicit-globals

Disallow variable and function declarations in the global scope

no-implied-eval

Disallow the use of eval()-like methods

no-invalid-this

Disallow this keywords outside of classes or class-like objects

no-iterator

Disallow the use of the __iterator__ property

no-labels

Disallow labeled statements

no-lone-blocks

Disallow unnecessary nested blocks

no-loop-func

Disallow function declarations and expressions inside loop statements

no-magic-numbers

Disallow magic numbers

no-multi-spaces

Disallow multiple spaces

no-multi-str

Disallow multiline strings

no-new

Disallow new operators outside of assignments or comparisons

no-new-func

Disallow new operators with the Function object

no-new-wrappers

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

no-octal

Disallow octal literals

no-octal-escape

Disallow octal escape sequences in string literals

no-param-reassign

Disallow reassigning function parameters

no-proto

Disallow the use of the __proto__ property

no-redeclare

Disallow variable redeclaration

no-restricted-properties

Disallow certain properties on certain objects

no-return-await

Disallow unnecessary return await

no-script-url

Disallow javascript: urls

no-return-assign

Disallow assignment operators in return statements

no-self-assign

Disallow assignments where both sides are exactly the same

no-self-compare

Disallow comparisons where both sides are exactly the same

no-sequences

Disallow comma operators

no-throw-literal

Disallow throwing literals as exceptions

no-unmodified-loop-condition

Disallow unmodified loop conditions

no-unused-labels

Disallow unused labels

no-unused-expressions

Disallow unused expressions

no-useless-call

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

no-useless-catch

Disallow unnecessary catch clauses

no-useless-concat

Disallow unnecessary concatenation of literals or template literals

no-useless-escape

Disallow unnecessary escape characters

no-useless-return

Disallow redundant return statements

no-void

Disallow void operators

no-warning-comments

Disallow specified warning terms in comments

no-with

Disallow with statements

prefer-promise-reject-errors

Require using Error objects as Promise rejection reasons

radix

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

require-await

Disallow async functions which have no await expression

require-unicode-regexp

Enforce the use of u flag on RegExp

vars-on-top

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

wrap-iife

Require parentheses around immediate function invocations

yoda

Require or disallow “Yoda” conditions

Strict Mode

Variables

Node.js and CommonJS

Stylistic Issues

ECMAScript 6

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no-useless-escape

- Disallow unnecessary escape characters

This rule flags escapes that can be safely removed without changing behavior.

What ESLint should do when it catches the rule break

Show a warning

Rule examples

You can check them out here.

no-useless-concat no-useless-return