Typescript類型體操 - Without

題目

中文

實現一個像 Lodash.without 函數一樣的泛型 Without<T, U>，它接收數組類型的 T 和數字或數組類型的 U 爲參數，會返回一個去除 U 中元素的數組 T。

例如：

type Res = Without<[1, 2], 1>; // expected to be [2]
type Res1 = Without<[1, 2, 4, 1, 5], [1, 2]>; // expected to be [4, 5]
type Res2 = Without<[2, 3, 2, 3, 2, 3, 2, 3], [2, 3]>; // expected to be []

English

Implement the type version of Lodash.without, Without<T, U> takes an Array T, number or array U and returns an Array without the elements of U.

type Res = Without<[1, 2], 1>; // expected to be [2]
type Res1 = Without<[1, 2, 4, 1, 5], [1, 2]>; // expected to be [4, 5]
type Res2 = Without<[2, 3, 2, 3, 2, 3, 2, 3], [2, 3]>; // expected to be []

答案

type Without<T extends any[], U extends any[] | number> = U extends number
    ? Without<T, [U]>
    : T extends [infer L, ...infer R]
    ? [
          ...(U extends [infer UL, ...infer UR]
              ? L extends UL
                  ? []
                  : Without<[L], UR>
              : [L]),
          ...Without<R, U>
      ]
    : [];

在線演示