目的

Github上的类型体操，让你写出更加优雅的TS类型定义，以及探寻TS中我们不熟悉的只是，让我们开始TS的类型挑战把~2022希望通过更文的方式来督促自己学习，每日三题，坚持日更不断~~

ts 类型体操 github 我的解答

题目大纲

1. Easy Includes
2. Easy Push
3. Easy Unshift

01. Easy Includes

题目要求

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

type cases = [
  Expect<Equal<Includes<['Kars', 'Esidisi', 'Wamuu', 'Santana'], 'Kars'>, true>>,
  Expect<Equal<Includes<['Kars', 'Esidisi','Wamuu', 'Santana'], 'Dio'>, false>>,
  Expect<Equal<Includes<[1, 2, 3, 5, 6, 7], 7>, true>>,
  Expect<Equal<Includes<[1, 2, 3, 5, 6, 7], 4>, false>>,
  Expect<Equal<Includes<[1, 2, 3], 2>, true>>,
  Expect<Equal<Includes<[1, 2, 3], 1>, true>>,
  Expect<Equal<Includes<[{}], { a: 'A' }>, false>>,
  Expect<Equal<Includes<[boolean, 2, 3, 5, 6, 7], false>, false>>,
  Expect<Equal<Includes<[true, 2, 3, 5, 6, 7], boolean>, false>>,
  Expect<Equal<Includes<[false, 2, 3, 5, 6, 7], false>, true>>,
  Expect<Equal<Includes<[{ a: 'A' }], { readonly a: 'A' }>, false>>,
  Expect<Equal<Includes<[{ readonly a: 'A' }], { a: 'A' }>, false>>,
]

我的答案

type Equal<X, Y> = (<T>() => T extends X ? 1 : 2) extends <T>() => T extends Y
  ? 1
  : 2
  ? true
  : false;

type Includes<T extends readonly any[], U> = T extends [
  infer First,
  ...infer Rest
]
  ? Equal<First, U> extends true
    ? true
    : Includes<Rest, U>
  : false;

知识点

1. 使用Equal的方法来进行判断，因为 false extends boolean的话直接用extends是没办法判断出来的

2. typescript也可以使用递归的方式，进行调用，比如这里在Includes中继续使用Includes

2. Easy Push

题目要求

import { Equal, Expect, ExpectFalse, NotEqual } from '@type-challenges/utils'

type cases = [
  Expect<Equal<Push<[], 1>, [1]>>,
  Expect<Equal<Push<[1, 2], '3'>, [1, 2, '3']>>,
  Expect<Equal<Push<['1', 2, '3'], boolean>, ['1', 2, '3', boolean]>>,

我的解答

type Push<T extends any[], U> = [...T, U]

知识点

A1. 如何合并数组元素

Q1. 使用...扩展符

3. Easy Unshift

题目要求

import { Equal, Expect, ExpectFalse, NotEqual } from '@type-challenges/utils'

type cases = [
  Expect<Equal<Unshift<[], 1>, [1]>>,
  Expect<Equal<Unshift<[1, 2], 0>, [0, 1, 2,]>>,
  Expect<Equal<Unshift<['1', 2, '3'],boolean>, [boolean, '1', 2, '3']>>,
]

我的解答

type Unshift<T extends any[], U> = [U, ...T]

知识点

1. 使用...运算符在typescript可以继承数组元素