30 lines
921 B
TypeScript
30 lines
921 B
TypeScript
/**
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Extract all required keys from the given type.
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This is useful when you want to create a new type that contains different type values for the required keys only or use the list of keys for validation purposes, etc...
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@example
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```
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import type {RequiredKeysOf} from 'type-fest';
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declare function createValidation<Entity extends object, Key extends RequiredKeysOf<Entity> = RequiredKeysOf<Entity>>(field: Key, validator: (value: Entity[Key]) => boolean): ValidatorFn;
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interface User {
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name: string;
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surname: string;
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luckyNumber?: number;
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}
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const validator1 = createValidation<User>('name', value => value.length < 25);
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const validator2 = createValidation<User>('surname', value => value.length < 25);
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```
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@category Utilities
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*/
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export type RequiredKeysOf<BaseType extends object> = Exclude<{
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[Key in keyof BaseType]: BaseType extends Record<Key, BaseType[Key]>
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? Key
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: never
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}[keyof BaseType], undefined>;
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