Use of a banned type detected JS-0296
Anti-pattern
Major
6 days ago
—
15 days old
Don't use
{} as a type. {} actually means "any non-nullish value".
- If you want a type meaning "any object", you probably want object instead.
- If you want a type meaning "any value", you probably want unknown instead.
- If you want a type meaning "empty object", you probably want Record<string, never> instead.
- If you really want a type meaning "any non-nullish value", you probably want NonNullable<unknown> instead1import type { CommonOldmarrWidgetDefinition } from "./common";
2
3// eslint-disable-next-line @typescript-eslint/no-empty-object-type
4export type OldmarrUsenetDefinition = CommonOldmarrWidgetDefinition<"usenet", {}>;Don't use
{} as a type. {} actually means "any non-nullish value".
- If you want a type meaning "any object", you probably want object instead.
- If you want a type meaning "any value", you probably want unknown instead.
- If you want a type meaning "empty object", you probably want Record<string, never> instead.
- If you really want a type meaning "any non-nullish value", you probably want NonNullable<unknown> instead1import type { CommonOldmarrWidgetDefinition } from "./common";
2
3// eslint-disable-next-line @typescript-eslint/no-empty-object-type
4export type OldmarrMediaServerDefinition = CommonOldmarrWidgetDefinition<"media-server", {}>;Don't use
{} as a type. {} actually means "any non-nullish value".
- If you want a type meaning "any object", you probably want object instead.
- If you want a type meaning "any value", you probably want unknown instead.
- If you want a type meaning "empty object", you probably want Record<string, never> instead.
- If you really want a type meaning "any non-nullish value", you probably want NonNullable<unknown> instead1import type { CommonOldmarrWidgetDefinition } from "./common";
2
3// eslint-disable-next-line @typescript-eslint/no-empty-object-type
4export type OldmarrDlspeedDefinition = CommonOldmarrWidgetDefinition<"dlspeed", {}>;Don't use
{} as a type. {} actually means "any non-nullish value".
- If you want a type meaning "any object", you probably want object instead.
- If you want a type meaning "any value", you probably want unknown instead.
- If you want a type meaning "empty object", you probably want Record<string, never> instead.
- If you really want a type meaning "any non-nullish value", you probably want NonNullable<unknown> instead1import type { CommonOldmarrWidgetDefinition } from "./common";
2
3// eslint-disable-next-line @typescript-eslint/no-empty-object-type
4export type OldmarrUsenetDefinition = CommonOldmarrWidgetDefinition<"usenet", {}>;Don't use
{} as a type. {} actually means "any non-nullish value".
- If you want a type meaning "any object", you probably want object instead.
- If you want a type meaning "any value", you probably want unknown instead.
- If you want a type meaning "empty object", you probably want Record<string, never> instead.
- If you really want a type meaning "any non-nullish value", you probably want NonNullable<unknown> instead1import type { CommonOldmarrWidgetDefinition } from "./common";
2
3// eslint-disable-next-line @typescript-eslint/no-empty-object-type
4export type OldmarrMediaServerDefinition = CommonOldmarrWidgetDefinition<"media-server", {}>;
Description
Some builtin types have aliases, some types are considered dangerous or harmful. It's often a good idea to ban certain types to help with consistency and safety.
It includes a set of "best practices", intended to provide safety and standardization in your codebase:
Don't use the upper-case primitive types, you should use the lower-case types for consistency.
Avoid the
Functiontype, as it provides little safety for the following reasons:- It provides no type safety when calling the value, which means it's easy to provide the wrong arguments.
- It accepts class declarations, which will fail when called, as they are called without the
newkeyword.
Avoid the
Objectand{}types, as they mean "any non-nullish value".- This is a point of confusion for many developers, who think it means "any object type".
Avoid the
objecttype, as it is currently hard to use due to not being able to assert that keys exist.
Bad Practice
// use of upper-case primitives
const str: String = 'foo';
const bool: Boolean = true;
const num: Number = 1;
const symb: Symbol = Symbol('foo');
// use a proper function type
const func: Function = () => 1;
// use safer object types
const lowerObj: object = {};
const capitalObj1: Object = 1;
const capitalObj2: Object = { a: 'string' };
const curly1: {} = 1;
const curly2: {} = { a: 'string' };
Recommended
// use lower-case primitives for consistency
const str: string = 'foo';
const bool: boolean = true;
const num: number = 1;
const symb: symbol = Symbol('foo');
// use a proper function type
const func: () => number = () => 1;
// use safer object types
const lowerObj: Record<string, unknown> = {};
const capitalObj1: number = 1;
const capitalObj2: { a: string } = { a: 'string' };
const curly1: number = 1;
const curly2: Record<'a', string> = { a: 'string' };