58 lines
1.6 KiB
TypeScript
58 lines
1.6 KiB
TypeScript
import type {IsEqual} from './internal';
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/**
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Filter out keys from an object.
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Returns `never` if `Exclude` is strictly equal to `Key`.
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Returns `never` if `Key` extends `Exclude`.
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Returns `Key` otherwise.
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@example
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```
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type Filtered = Filter<'foo', 'foo'>;
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//=> never
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```
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@example
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```
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type Filtered = Filter<'bar', string>;
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//=> never
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```
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@example
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```
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type Filtered = Filter<'bar', 'foo'>;
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//=> 'bar'
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```
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@see {Except}
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*/
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type Filter<KeyType, ExcludeType> = IsEqual<KeyType, ExcludeType> extends true ? never : (KeyType extends ExcludeType ? never : KeyType);
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/**
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Create a type from an object type without certain keys.
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This type is a stricter version of [`Omit`](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-5.html#the-omit-helper-type). The `Omit` type does not restrict the omitted keys to be keys present on the given type, while `Except` does. The benefits of a stricter type are avoiding typos and allowing the compiler to pick up on rename refactors automatically.
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This type was proposed to the TypeScript team, which declined it, saying they prefer that libraries implement stricter versions of the built-in types ([microsoft/TypeScript#30825](https://github.com/microsoft/TypeScript/issues/30825#issuecomment-523668235)).
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@example
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```
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import type {Except} from 'type-fest';
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type Foo = {
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a: number;
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b: string;
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c: boolean;
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};
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type FooWithoutA = Except<Foo, 'a' | 'c'>;
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//=> {b: string};
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```
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@category Object
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*/
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export type Except<ObjectType, KeysType extends keyof ObjectType> = {
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[KeyType in keyof ObjectType as Filter<KeyType, KeysType>]: ObjectType[KeyType];
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};
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