consistent-type-definitions

Enforces type definitions to consistently use either interface or type.

There are two ways to define a type.

// type alias
type T1 = {
  a: string;
  b: number;
};

// interface keyword
interface T2 {
  a: string;
  b: number;
}

Attributes

• Included in configs
  • ✅ Recommended
  • 🔒 Strict
• Fixable
  • 🔧 Automated Fixer
  • 🛠 Suggestion Fixer
• 💭 Requires type information

Options

This rule accepts one string option:

• "interface": enforce using interfaces for object type definitions.
• "type": enforce using types for object type definitions.

For example:

{
  // Use type for object definitions
  "@typescript-eslint/consistent-type-definitions": ["error", "type"]
}

interface

Examples of code with interface option.

❌ Incorrect

type T = { x: number };

✅ Correct

type T = string;
type Foo = string | {};

interface T {
  x: number;
}

type

Examples of code with type option.

❌ Incorrect

interface T {
  x: number;
}

✅ Correct

type T = { x: number };

When Not To Use It

If you specifically want to use an interface or type literal for stylistic reasons, you can disable this rule.