sort-maps

Enforce sorted elements within JavaScript Map object.

Sorting elements within JavaScript Map objects provides a clear and predictable structure to the codebase. This rule detects instances where Map elements are not sorted and raises linting errors, encouraging developers to arrange elements in the desired order.

By maintaining a consistent structure across Map objects, this rule improves readability and makes it easier to locate and understand key-value pairs.

Try it out

const products = new Map([
  ['monitor', { name: 'Monitor', price: 200 }],
  ['laptop', { name: 'Laptop', price: 1000 }],
  ['mouse', { name: 'Mouse', price: 25 }],
  ['keyboard', { name: 'Keyboard', price: 50 }],
])

const categories = new Map([
  ['electronics', { name: 'Electronics' }],
  ['furniture', { name: 'Furniture' }],
  ['clothing', { name: 'Clothing' }],
  ['accessories', { name: 'Accessories' }],
])

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 maps into logical groups. This can help in organizing and maintaining large maps 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 map if there is an empty line between them. This helps maintain the defined order of logically separated groups of members.

new Map([
     // Group 1
    ['Drone', 0],
    ['Keyboard', 1],
    ['Mouse', 3],
    ['Smartphone', 4],

    // Group 2
    ['Laptop', 5],
    ['Monitor', 6],
    ['Smartwatch', 7],
    ['Tablet', 8],

    // Group 3
    ['Headphones', 9],
    ['Router', 10],
  ])

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

newlinesBetween

_{default: 'ignore'}

Specifies how to handle new lines between map members.

ignore — Do not report errors related to new lines between map members.
always — Enforce one new line between each group, and forbid new lines inside a group.
never — No new lines are allowed in maps.

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.

useConfigurationIf

_{type:
{
allNamesMatchPattern?: string | string[] | { pattern: string; flags: string } | { pattern: string; flags: string }[]
}}_{default: {}}

Specifies filters to match a particular options configuration for a given map.

The first matching options configuration will be used. If no configuration matches, the default options configuration will be used.

allNamesMatchPattern — A regexp pattern that all map keys must match.

Example configuration:

{
  'perfectionist/sort-maps': [
    'error',
    {
      groups: ['r', 'g', 'b'], // Sort colors by RGB
      customGroups: [
        {
          elementNamePattern: '^r$',
          groupName: 'r',
        },
        {
          elementNamePattern: '^g$',
          groupName: 'g',
        },
        {
          elementNamePattern: '^b$',
          groupName: 'b',
        },
      ],
      useConfigurationIf: {
        allNamesMatchPattern: '^r|g|b$',
      },
    },
    {
      type: 'alphabetical' // Fallback configuration
    }
  ],
}

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.

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: 'always',
  groups: [
    'a',
    { newlinesBetween: 'never' }, // Overrides the global newlinesBetween option
    'b',
  ]
}

customGroups

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

Defines custom groups to match specific elements.

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?: 'always' | 'never'
  elementNamePattern?: string | string[] | { pattern: string; flags?: string } | { pattern: string; flags?: string }[]
}

A map element 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?: 'always' | 'never'
  anyOf: Array<{
      elementNamePattern?: string | string[] | { pattern: string; flags?: string } | { pattern: string; flags?: string }[]
  }>
}

A map element 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.
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-maps': [
      'error',
      {
        type: 'alphabetical',
        order: 'asc',
        fallbackSort: { type: 'unsorted' },
        ignoreCase: true,
        specialCharacters: 'keep',
        partitionByNewLine: false,
        partitionByComment: false,
        newlinesBetween: false,
        useConfigurationIf: {},
        groups: [],
        customGroups: [],
      },
    ],
  },
}

Version

This rule was introduced in v0.5.0.