Possible Errors

Best Practices

Strict Mode

Variables

Node.js and CommonJS

Stylistic Issues

array-bracket-newline

Enforce linebreaks after opening and before closing array brackets

array-bracket-spacing

Enforce consistent spacing inside array brackets

array-element-newline

Enforce line breaks after each array element

block-spacing

Disallow or enforce spaces inside of blocks after opening block and before closing block

brace-style

Enforce consistent brace style for blocks

camelcase

Enforce camelcase naming convention

capitalized-comments

Enforce or disallow capitalization of the first letter of a comment

comma-dangle

Require or disallow trailing commas

comma-spacing

Enforce consistent spacing before and after commas

comma-style

Enforce consistent comma style

computed-property-spacing

Enforce consistent spacing inside computed property brackets

consistent-this

Enforce consistent naming when capturing the current execution context

eol-last

Require or disallow newline at the end of files

func-call-spacing

Require or disallow spacing between function identifiers and their invocations

func-name-matching

Require function names to match the name of the variable or property to which they are assigned

func-names

Require or disallow named function expressions

func-style

Enforce the consistent use of either function declarations or expressions

function-paren-newline

Enforce consistent line breaks inside function parentheses

id-blacklist

Disallow specified identifiers

id-length

Enforce minimum and maximum identifier lengths

id-match

Require identifiers to match a specified regular expression

implicit-arrow-linebreak

Enforce the location of arrow function bodies

indent

Enforce consistent indentation

jsx-quotes

Enforce the consistent use of either double or single quotes in JSX attributes

key-spacing

Enforce consistent spacing between keys and values in object literal properties

keyword-spacing

Enforce consistent spacing before and after keywords

line-comment-position

Enforce position of line comments

linebreak-style

Enforce consistent linebreak style

lines-around-comment

Require empty lines around comments

lines-between-class-members

Require or disallow an empty line between class members

max-depth

Enforce a maximum depth that blocks can be nested

max-len

Enforce a maximum line length

max-lines

Enforce a maximum number of lines per file

max-lines-per-function

Enforce a maximum number of line of code in a function

max-nested-callbacks

Enforce a maximum depth that callbacks can be nested

max-params

Enforce a maximum number of parameters in function definitions

max-statements

Enforce a maximum number of statements allowed in function blocks

max-statements-per-line

Enforce a maximum number of statements allowed per line

multiline-comment-style

Enforce a particular style for multiline comments

multiline-ternary

Enforce newlines between operands of ternary expressions

new-cap

Require constructor names to begin with a capital letter

new-parens

Require parentheses when invoking a constructor with no arguments

newline-per-chained-call

Require a newline after each call in a method chain

no-array-constructor

Disallow Array constructors

no-bitwise

Disallow bitwise operators

no-continue

Disallow continue statements

no-inline-comments

Disallow inline comments after code

no-lonely-if

Disallow if statements as the only statement in else blocks

no-mixed-operators

Disallow mixed binary operators

no-mixed-spaces-and-tabs

Disallow mixed spaces and tabs for indentation

no-multi-assign

Disallow use of chained assignment expressions

no-multiple-empty-lines

Disallow multiple empty lines

no-negated-condition

Disallow negated conditions

no-nested-ternary

Disallow nested ternary expressions

no-new-object

Disallow Object constructors

no-plusplus

Disallow the unary operators ++ and --

no-restricted-syntax

Disallow specified syntax

no-tabs

Disallow all tabs

no-ternary

Disallow ternary operators

no-trailing-spaces

Disallow trailing whitespace at the end of lines

no-underscore-dangle

Disallow dangling underscores in identifiers

no-unneeded-ternary

Disallow ternary operators when simpler alternatives exist

no-whitespace-before-property

Disallow whitespace before properties

nonblock-statement-body-position

Enforce the location of single-line statements

object-curly-newline

Enforce consistent line breaks inside braces

object-curly-spacing

Enforce consistent spacing inside braces

object-property-newline

Enforce placing object properties on separate lines

one-var

Enforce variables to be declared either together or separately in functions

one-var-declaration-per-line

Require or disallow newlines around variable declarations

operator-assignment

Require or disallow assignment operator shorthand where possible

operator-linebreak

Enforce consistent linebreak style for operators

padded-blocks

Require or disallow padding within blocks

padding-line-between-statements

Require or disallow padding lines between statements

prefer-object-spread

Disallow using Object.assign with an object literal as the first argument and prefer the use of object spread instead

quote-props

Require quotes around object literal property names

quotes

Enforce the consistent use of either backticks, double, or single quotes

require-jsdoc

Require JSDoc comments

semi

Require or disallow semicolons instead of ASI

semi-spacing

Enforce consistent spacing before and after semicolons

semi-style

Enforce location of semicolons

sort-keys

Require object keys to be sorted

sort-vars

Require variables within the same declaration block to be sorted

space-before-blocks

Enforce consistent spacing before blocks

space-before-function-paren

Enforce consistent spacing before function definition opening parenthesis

space-in-parens

Enforce consistent spacing inside parentheses

space-infix-ops

Require spacing around infix operators

space-unary-ops

Enforce consistent spacing before or after unary operators

spaced-comment

Enforce consistent spacing after the // or /* in a comment

switch-colon-spacing

Enforce spacing around colons of switch statements

template-tag-spacing

Require or disallow spacing between template tags and their literals

unicode-bom

Require or disallow Unicode byte order mark (BOM)

wrap-regex

Require parenthesis around regex literals

ECMAScript 6

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space-before-function-paren

- Enforce consistent spacing before function definition opening parenthesis

This rule aims to enforce consistent spacing before function parentheses and as such, will warn whenever whitespace doesn’t match the preferences specified.

What ESLint should do when it catches the rule break

Show a warning

Options

always

Rule examples

You can check them out here.

space-before-blocks space-in-parens