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-unused-expressions

- Disallow unused expressions

This rule aims to eliminate unused expressions which have no effect on the state of the program.

What ESLint should do when it catches the rule break

Show a warning

Options

allowShortCircuit

Allows to use short circuit evaluations in the expressions.

allowTernary

Allows to use ternary operators in the expressions similarly to short circuit evaluations.

allowTaggedTemplates

Allows to use tagged template literals in the expressions.

Rule examples

You can check them out here.

no-unused-labels no-useless-call