51 lines
1.2 KiB
Plaintext
51 lines
1.2 KiB
Plaintext
/**
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Pick only index signatures from the given object type, leaving out all explicitly defined properties.
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This is the counterpart of `OmitIndexSignature`.
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@example
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```
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import type {PickIndexSignature} from 'type-fest';
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declare const symbolKey: unique symbol;
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type Example = {
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// These index signatures will remain.
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[x: string]: unknown;
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[x: number]: unknown;
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[x: symbol]: unknown;
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[x: `head-${string}`]: string;
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[x: `${string}-tail`]: string;
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[x: `head-${string}-tail`]: string;
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[x: `${bigint}`]: string;
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[x: `embedded-${number}`]: string;
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// These explicitly defined keys will be removed.
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['kebab-case-key']: string;
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[symbolKey]: string;
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foo: 'bar';
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qux?: 'baz';
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};
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type ExampleIndexSignature = PickIndexSignature<Example>;
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// {
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// [x: string]: unknown;
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// [x: number]: unknown;
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// [x: symbol]: unknown;
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// [x: `head-${string}`]: string;
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// [x: `${string}-tail`]: string;
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// [x: `head-${string}-tail`]: string;
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// [x: `${bigint}`]: string;
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// [x: `embedded-${number}`]: string;
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// }
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```
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@see OmitIndexSignature
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@category Object
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*/
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export type PickIndexSignature<ObjectType> = {
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[KeyType in keyof ObjectType as {} extends Record<KeyType, unknown>
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? KeyType
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: never]: ObjectType[KeyType];
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};
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