33. Absolute

[astak16]

题目

题目链接：Absolute，答题

实现 Absoulte 类型，接收 string、number、bigint 类型，返回一个整数字符串

import type { Equal, Expect } from "@type-challenges/utils";

type cases = [
  Expect<Equal<Absolute<0>, "0">>,
  Expect<Equal<Absolute<-0>, "0">>,
  Expect<Equal<Absolute<10>, "10">>,
  Expect<Equal<Absolute<-5>, "5">>,
  Expect<Equal<Absolute<"0">, "0">>,
  Expect<Equal<Absolute<"-0">, "0">>,
  Expect<Equal<Absolute<"10">, "10">>,
  Expect<Equal<Absolute<"-5">, "5">>,
  Expect<Equal<Absolute<-1_000_000n>, "1000000">>,
  Expect<Equal<Absolute<9_999n>, "9999">>
];

答案

下面三个方法的思路都是一样的

• bigint 和 number 类型通过 ${T} 可以变成 string 类型
  • 1_000_000n = "1000000"
• 把负数变成正数
  • -{infer S}，S 就是正数

方法一

type ToString<T extends string | number | bigint> = `${T}`;
type Absolute<T extends string | number | bigint> =
  ToString<T> extends `${infer P}${infer S}`
    ? P extends "-"
      ? S
      : ToString<T>
    : ToString<T>;

方法二

type ToString<T extends string | number | bigint> = `${T}`;
type Absolute<T extends string | number | bigint> = T extends string
  ? T extends `-${infer S}`
    ? S
    : T
  : Absolute<ToString<T>>;

方法三

type ToString<T extends string | number | bigint> = `${T}`;
type Absolute<T extends string | number | bigint> =
  ToString<T> extends `-${infer S}` ? S : ToString<T>;