Constant Rules

Rules that govern how readonly constant files are written. Every rule is enabled by the recommended config and applies to .ts / .tsx files inside a /constants/ folder of your project.

constant-naming-convention

Require readonly constant names to use UPPERCASE_SNAKE_CASE — uppercase letters, digits, and underscores, with an uppercase first character.

const API = {
  path: '/api/v1/',
  port: '4000'
}

export default API

const apiConfig = {
  path: '/api/v1/',
  port: '4000'
}

export default apiConfig

The rule only checks top-level const declarations in /constants/ files, and it focuses on the default-exported constant (or the only one if there is no default export yet).

constant-single-object

Require constant files to group values into a single top-level object.

const API = {
  path: '/api/v1/',
  port: '4000'
}

export default API

const API_PATH = '/api/v1/'

export default API_PATH

A single object makes the default export obvious and keeps related values together. Primitive constants or multiple top-level objects in the same file are rejected.

constant-filename-matches-name

Require constant file names to match constant names (excluding extension).

const API = {
  path: '/api/v1/',
  port: '4000'
}

export default API

const API_CONFIG = {
  path: '/api/v1/',
  port: '4000'
}

export default API_CONFIG

A matching file name keeps the import path and the constant name in lockstep, which matters a lot for constants that are used in many places.

constant-require-default-export

Require constant files to default export their constants object.

const API = {
  path: '/api/v1/',
  port: '4000'
}

export default API

const API = {
  path: '/api/v1/',
  port: '4000'
}

export { API }

The equivalent export { Name as default } form is also accepted:

const API = {
  path: '/api/v1/',
  port: '4000'
}

export { API as default }