DMleadgen
46d973904b
Next.js website for Rocky Mountain Vending company featuring: - Product catalog with Stripe integration - Service areas and parts pages - Admin dashboard with Clerk authentication - SEO optimized pages with JSON-LD structured data Co-authored-by: Cursor <cursoragent@cursor.com>
51 lines
1.7 KiB
Text
51 lines
1.7 KiB
Text
/**
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Convert a tuple/array into a union type of its elements.
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This can be useful when you have a fixed set of allowed values and want a type defining only the allowed values, but do not want to repeat yourself.
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@example
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```
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import type {TupleToUnion} from 'type-fest';
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const destinations = ['a', 'b', 'c'] as const;
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type Destination = TupleToUnion<typeof destinations>;
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//=> 'a' | 'b' | 'c'
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function verifyDestination(destination: unknown): destination is Destination {
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return destinations.includes(destination as any);
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}
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type RequestBody = {
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deliverTo: Destination;
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};
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function verifyRequestBody(body: unknown): body is RequestBody {
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const deliverTo = (body as any).deliverTo;
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return typeof body === 'object' && body !== null && verifyDestination(deliverTo);
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}
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```
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Alternatively, you may use `typeof destinations[number]`. If `destinations` is a tuple, there is no difference. However if `destinations` is a string, the resulting type will the union of the characters in the string. Other types of `destinations` may result in a compile error. In comparison, TupleToUnion will return `never` if a tuple is not provided.
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@example
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```
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const destinations = ['a', 'b', 'c'] as const;
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type Destination = typeof destinations[number];
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//=> 'a' | 'b' | 'c'
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const erroringType = new Set(['a', 'b', 'c']);
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type ErroringType = typeof erroringType[number];
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//=> Type 'Set<string>' has no matching index signature for type 'number'. ts(2537)
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const numberBool: { [n: number]: boolean } = { 1: true };
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type NumberBool = typeof numberBool[number];
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//=> boolean
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```
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@category Array
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*/
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export type TupleToUnion<ArrayType> = ArrayType extends readonly unknown[] ? ArrayType[number] : never;
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