【Typescirpt】定義數字范圍類型

數字范圍參數

有的時候我們想定義一個參數的數字范圍，如果范圍比較小點好，比如1到5。

type Range = 1 | 2 | 3 | 4 | 5 ;

但如果數字范圍很大，比如 1到100，或是1到1000，那就要寫死了。

支持現狀

Github上有人提了相關的建議，但還處於Open狀態
https://github.com/microsoft/TypeScript/issues/15480

現實

從網上找抄了一個別的人實現的(Playground)：

type BuildPowersOf2LengthArrays<N extends number, R extends never[][]> =
  R[0][N] extends never ? R : BuildPowersOf2LengthArrays<N, [[...R[0], ...R[0]], ...R]>;

type ConcatLargestUntilDone<N extends number, R extends never[][], B extends never[]> =
  B["length"] extends N ? B : [...R[0], ...B][N] extends never
    ? ConcatLargestUntilDone<N, R extends [R[0], ...infer U] ? U extends never[][] ? U : never : never, B>
    : ConcatLargestUntilDone<N, R extends [R[0], ...infer U] ? U extends never[][] ? U : never : never, [...R[0], ...B]>;

type Replace<R extends any[], T> = { [K in keyof R]: T }

type TupleOf<T, N extends number> = number extends N ? T[] : {
  [K in N]: 
  BuildPowersOf2LengthArrays<K, [[never]]> extends infer U ? U extends never[][]
  ? Replace<ConcatLargestUntilDone<K, U, []>, T> : never : never;
}[N]

type RangeOf<N extends number> = Partial<TupleOf<unknown, N>>["length"];

type RangeOf2<From extends number, To extends number> = Exclude<RangeOf<To>, RangeOf<From>> | From;

type X = RangeOf2<1,100>