@typescript-eslint/array-type

string[] and Array<string> are the same type. A codebase that mixes the two makes readers stop and check whether the difference means something. This rule picks one. By default it's T[], and readonly T[] for read-only arrays.

--fix rewrites the type to the other form.

Configure#

Off by default. To turn it on:

bunfig.toml

[lint.rules]
"@typescript-eslint/array-type" = "error" # or "warn"

Every option, set to its default. The ones that are commented out are unset by default.

bunfig.toml

[lint.rules]
"@typescript-eslint/array-type" = ["error", {
  default = "array", # "array", "generic" or "array-simple"
  # readonly = <"array", "generic" or "array-simple">,
}]

Examples#

example.ts2 problems

const names: Array<string> = [];
const ids: ReadonlyArray<number> = [1, 2];

example.tsNo problems

const names: string[] = [];
const ids: readonly number[] = [1, 2];

Options#

Option	Default	What it does
`default`	`"array"`	The form for arrays you can change.
`readonly`	the value of `default`	The form for read-only arrays.

Each takes one of these values:

Value	What it does
`"array"`	Require `T[]` and `readonly T[]`.
`"generic"`	Require `Array<T>` and `ReadonlyArray<T>`.
`"array-simple"`	Require `T[]` when `T` is simple, and `Array<T>` when it isn't.

A simple type is a keyword such as string, a name without type arguments such as User, or an array. Unions, functions, object types, and generics aren't simple.

example.tswith { "default": "generic" }1 problem

const names: string[] = [];

With "array-simple", both lines are reported:

example.tswith { "default": "array-simple" }2 problems

const names: Array<string> = [];
const values: (string | number)[] = [];

example.tswith { "default": "array-simple" }No problems

const names: string[] = [];
const values: Array<string | number> = [];

readonly can differ from default:

example.tswith { "default": "array", "readonly": "generic" }No problems

const names: string[] = [];
const ids: ReadonlyArray<number> = [1, 2];