sort-variable-declarations

Enforce sorted variable declarations within a scope.

Variable declarations within a block of code can quickly become disorganized and difficult to navigate, especially in larger functions or modules. With this rule, you can ensure that all variable declarations are consistently sorted, making it easier to locate specific variables and maintain a clean and structured codebase.

This practice improves readability and maintainability by providing a predictable order for variable declarations. It helps developers quickly understand the scope and usage of variables without having to search through an unsorted list.

Try it out

const data = fetchData(),
      isAuthenticated = checkAuth(),
      API_KEY = 'e7c3b6d4-7b7d-4b3b-8b3b-7b3b7b3b7b3b',
      user = getCurrentUser(),
      apiUrl = 'https://api.perfectionist.dev'

const logger = createLogger(),
      database = connectToDatabase(),
      config = loadConfig(),
      environment = process.env.NODE_ENV,
      server = createServer()

Options

This rule accepts an options object with the following properties:

type

_{default: 'alphabetical'}

Specifies the sorting method.

'alphabetical' — Sort items alphabetically (e.g., “a” < “b” < “c”) using localeCompare.
'natural' — Sort items in a natural order (e.g., “item2” < “item10”).
'line-length' — Sort items by code line length (shorter lines first).
'custom' — Sort items using the alphabet specified in the alphabet option.
'unsorted' — Do not sort items. grouping and newlines behavior are still enforced.

order

_{default: 'asc'}

Specifies whether to sort items in ascending or descending order.

'asc' — Sort items in ascending order (A to Z, 1 to 9).
'desc' — Sort items in descending order (Z to A, 9 to 1).

fallbackSort

_{type:
{
type: 'alphabetical' | 'natural' | 'line-length' | 'custom' | 'unsorted'
order?: 'asc' | 'desc'
}}_{default: { type: 'unsorted' }}

Specifies fallback sort options for elements that are equal according to the primary sort type.

Example: enforce alphabetical sort between two elements with the same length.

{
  type: 'line-length',
  order: 'desc',
  fallbackSort: { type: 'alphabetical', order: 'asc' }
}

alphabet

_{default: ''}

Used only when the type option is set to 'custom'. Specifies the custom alphabet for sorting.

Use the Alphabet utility class from eslint-plugin-perfectionist/alphabet to quickly generate a custom alphabet.

Example: 0123456789abcdef...

ignoreCase

_{default: true}

Specifies whether sorting should be case-sensitive.

true — Ignore case when sorting alphabetically or naturally (e.g., “A” and “a” are the same).
false — Consider case when sorting (e.g., “a” comes before “A”).

specialCharacters

_{default: keep}

Specifies whether to trim, remove, or keep special characters before sorting.

'keep' — Keep special characters when sorting (e.g., “_a” comes before “a”).
'trim' — Trim special characters when sorting alphabetically or naturally (e.g., “_a” and “a” are the same).
'remove' — Remove special characters when sorting (e.g., “/a/b” and “ab” are the same).

locales

_{default: 'en-US'}

Specifies the sorting locales. Refer To String.prototype.localeCompare() - locales.

string — A BCP 47 language tag (e.g. 'en', 'en-US', 'zh-CN').
string[] — An array of BCP 47 language tags.

partitionByComment

_{default: false}

Enables the use of comments to separate the members of variable declarations into logical groups. This can help in organizing and maintaining large variable declaration blocks by creating partitions based on comments.

true — All comments will be treated as delimiters, creating partitions.
false — Comments will not be used as delimiters.
RegExpPattern = string | { pattern: string; flags: string} — A regexp pattern to specify which comments should act as delimiters.
RegExpPattern[] — A list of regexp patterns to specify which comments should act as delimiters.
{ block: boolean | RegExpPattern | RegExpPattern[]; line: boolean | RegExpPattern | RegExpPattern[] } — Specify which block and line comments should act as delimiters.

partitionByNewLine

_{default: false}

When true, the rule will not sort the members of a variable declaration if there is an empty line between them. This helps maintain the defined order of logically separated groups of members.

const
  // Group 1
  fiat = "Fiat",
  honda = "Honda",

  // Group 2
  ferrari = "Ferrari",

  // Group 3
  chevrolet = "Chevrolet",
  ford = "Ford"

Each group of variables (separated by empty lines) is treated independently, and the order within each group is preserved.

newlinesBetween

_{type: number | 'ignore'}_{default: 'ignore'}

Specifies how to handle newlines between groups.

'ignore' — Do not report errors related to newlines.
0 — No newlines are allowed.
Any other number — Enforce this number of newlines between each group, and forbid newlines inside groups.

You can also enforce the newline behavior between two specific groups through the groups options.

See the groups option.

This option is only applicable when partitionByNewLine is false.

groups

_{type: Array<string | string[]>}_{default: []}

Specifies a list of groups for sorting. Groups help organize elements into categories.

Each element will be assigned a single group specified in the groups option (or the unknown group if no match is found). The order of items in the groups option determines how groups are ordered.

Within a given group, members will be sorted according to the type, order, ignoreCase, etc. options.

Individual groups can be combined together by placing them in an array. The order of groups in that array does not matter. All members of the groups in the array will be sorted together as if they were part of a single group.

Predefined groups are characterized by a selector.

List of selectors

initialized — Initialized declarations.
uninitialized — Uninitialized declarations.

Newlines between groups

You may place newlinesBetween objects between your groups to enforce the newline behavior between two specific groups.

See the newlinesBetween option.

This feature is only applicable when partitionByNewLine is false.

{
  newlinesBetween: 1,
  groups: [
    'a',
    { newlinesBetween: 0 }, // Overrides the global newlinesBetween option
    'b',
  ]
}

customGroups

_{type: Array<CustomGroupDefinition | CustomGroupAnyOfDefinition>}_{default: []}

Defines custom groups to match specific object type members.

A custom group definition may follow one of the two following interfaces:

interface CustomGroupDefinition {
  groupName: string
  type?: 'alphabetical' | 'natural' | 'line-length' | 'unsorted'
  order?: 'asc' | 'desc'
  fallbackSort?: { type: string; order?: 'asc' | 'desc' }
  newlinesInside?: number
  selector?: string
  elementNamePattern?: string | string[] | { pattern: string; flags?: string } | { pattern: string; flags?: string }[]
}

A declaration will match a CustomGroupDefinition group if it matches all the filters of the custom group’s definition.

or:

interface CustomGroupAnyOfDefinition {
  groupName: string
  type?: 'alphabetical' | 'natural' | 'line-length' | 'unsorted'
  order?: 'asc' | 'desc'
  fallbackSort?: { type: string; order?: 'asc' | 'desc' }
  newlinesInside?: number
  anyOf: Array<{
      selector?: string
      elementNamePattern?: string | string[] | { pattern: string; flags?: string } | { pattern: string; flags?: string }[]
  }>
}

A declaration will match a CustomGroupAnyOfDefinition group if it matches all the filters of at least one of the anyOf items.

Attributes

groupName — The group’s name, which needs to be put in the groups option.
selector — Filter on the selector of the element.
elementNamePattern — If entered, will check that the name of the element matches the pattern entered.
type — Overrides the type option for that custom group. unsorted will not sort the group.
order — Overrides the order option for that custom group.
fallbackSort — Overrides the fallbackSort option for that custom group.
newlinesInside — Enforces a specific newline behavior between elements of the group.

Match importance

The customGroups list is ordered: The first custom group definition that matches an element will be used.

Custom groups have a higher priority than any predefined group.

Usage

// .eslintrc.js
module.exports = {
  plugins: [
    'perfectionist',
  ],
  rules: {
    'perfectionist/sort-variable-declarations': [
      'error',
      {
        type: 'alphabetical',
        order: 'asc',
        fallbackSort: { type: 'unsorted' },
        ignoreCase: true,
        specialCharacters: 'keep',
        partitionByNewLine: false,
        partitionByComment: false,
        newlinesBetween: 'ignore',
        groups: [],
        customGroups: [],
      },
    ],
  },
}

Version

This rule was introduced in v3.0.0.