indexedObjectTypes

Reports indexed object types that don't match the configured style.

✅ This rule is included in the ts stylistic presets.

TypeScript provides two equivalent ways to define indexed object types: Record<K, V> and { [key: K]: V }. Using one style consistently improves code readability.

This rule enforces consistent usage of either Record<K, V> (default) or index signatures.

Examples

❌ Incorrect

interface Data {
  [key: string]: number;
}

type StringMap = { [key: string]: string };

function process(data: { [key: string]: number }): void {}

✅ Correct

type Data = Record<string, number>;

type StringMap = Record<string, string>;

function process(data: Record<string, number>): void {}

Options

style

• "record" (default): Prefer Record<K, V> over index signatures.
• "index-signature": Prefer index signatures over Record<K, V>.

When set to "index-signature":

❌ Incorrect

type Data = Record<string, number>;

✅ Correct

type Data = { [key: string]: number };

When Not To Use It

If your project already has an established convention for indexed object types that you don’t want to enforce, or if you prefer allowing both styles for flexibility, you may disable this rule.

Further Reading

• TypeScript: Index Signatures
• TypeScript: Utility Types - Record

Equivalents in Other Linters

• ESLint: @typescript-eslint/consistent-indexed-object-style
• Oxlint: typescript/consistent-indexed-object-style