47 lines
1.5 KiB
Plaintext
47 lines
1.5 KiB
Plaintext
declare const emptyObjectSymbol: unique symbol;
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/**
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Represents a strictly empty plain object, the `{}` value.
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When you annotate something as the type `{}`, it can be anything except `null` and `undefined`. This means that you cannot use `{}` to represent an empty plain object ([read more](https://stackoverflow.com/questions/47339869/typescript-empty-object-and-any-difference/52193484#52193484)).
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@example
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```
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import type {EmptyObject} from 'type-fest';
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// The following illustrates the problem with `{}`.
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const foo1: {} = {}; // Pass
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const foo2: {} = []; // Pass
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const foo3: {} = 42; // Pass
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const foo4: {} = {a: 1}; // Pass
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// With `EmptyObject` only the first case is valid.
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const bar1: EmptyObject = {}; // Pass
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const bar2: EmptyObject = 42; // Fail
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const bar3: EmptyObject = []; // Fail
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const bar4: EmptyObject = {a: 1}; // Fail
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```
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Unfortunately, `Record<string, never>`, `Record<keyof any, never>` and `Record<never, never>` do not work. See {@link https://github.com/sindresorhus/type-fest/issues/395 #395}.
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@category Object
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*/
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export type EmptyObject = {[emptyObjectSymbol]?: never};
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/**
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Returns a `boolean` for whether the type is strictly equal to an empty plain object, the `{}` value.
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@example
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```
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import type {IsEmptyObject} from 'type-fest';
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type Pass = IsEmptyObject<{}>; //=> true
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type Fail = IsEmptyObject<[]>; //=> false
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type Fail = IsEmptyObject<null>; //=> false
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```
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@see EmptyObject
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@category Object
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*/
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export type IsEmptyObject<T> = T extends EmptyObject ? true : false;
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