[TypeScript] Type Challenges #1978 - Percentage Parser

题目描述

实现类型 PercentageParser。根据规则 /^(\+|\-)?(\d*)?(\%)?$/ 匹配类型 T。

匹配的结果由三部分组成，分别是：[正负号, 数字, 单位]，如果没有匹配，则默认是空字符串。

例如：

type PString1 = ''
type PString2 = '+85%'
type PString3 = '-85%'
type PString4 = '85%'
type PString5 = '85'

type R1 = PercentageParser<PString1> // expected ['', '', '']
type R2 = PercentageParser<PString2> // expected ["+", "85", "%"]
type R3 = PercentageParser<PString3> // expected ["-", "85", "%"]
type R4 = PercentageParser<PString4> // expected ["", "85", "%"]
type R5 = PercentageParser<PString5> // expected ["", "85", ""]

题解

// ============= Test Cases =============
import type { Equal, Expect } from './test-utils'

type Case0 = ['', '', '']
type Case1 = ['+', '', '']
type Case2 = ['+', '1', '']
type Case3 = ['+', '100', '']
type Case4 = ['+', '100', '%']
type Case5 = ['', '100', '%']
type Case6 = ['-', '100', '%']
type Case7 = ['-', '100', '']
type Case8 = ['-', '1', '']
type Case9 = ['', '', '%']
type Case10 = ['', '1', '']
type Case11 = ['', '100', '']

type cases = [
  Expect<Equal<PercentageParser<''>, Case0>>,
  Expect<Equal<PercentageParser<'+'>, Case1>>,
  Expect<Equal<PercentageParser<'+1'>, Case2>>,
  Expect<Equal<PercentageParser<'+100'>, Case3>>,
  Expect<Equal<PercentageParser<'+100%'>, Case4>>,
  Expect<Equal<PercentageParser<'100%'>, Case5>>,
  Expect<Equal<PercentageParser<'-100%'>, Case6>>,
  Expect<Equal<PercentageParser<'-100'>, Case7>>,
  Expect<Equal<PercentageParser<'-1'>, Case8>>,
  Expect<Equal<PercentageParser<'%'>, Case9>>,
  Expect<Equal<PercentageParser<'1'>, Case10>>,
  Expect<Equal<PercentageParser<'100'>, Case11>>,
]


// ============= Your Code Here =============
type ParseSign<T extends string> =
  T extends `${infer Sign extends '+' | '-'}${string}`
      ? Sign
      : '';

type ParseNumber<T extends string> =
  T extends `${ParseSign<T>}${infer Number}${ParsePersent<T>}`
      ? Number
      : '';

type ParsePersent<T extends string> =
  T extends `${string}${infer Unit extends '%'}`
      ? Unit
      : '';

type PercentageParser<T extends string> = [
  ParseSign<T>,
  ParseNumber<T>,
  ParsePersent<T>,
];

条件类型

type ParseSign<T extends string> =
  T extends `${infer Sign extends '+' | '-'}${string}`
      ? Sign
      : '';

type ParseNumber<T extends string> =
  T extends `${ParseSign<T>}${infer Number}${ParsePersent<T>}`
      ? Number
      : '';

type ParsePersent<T extends string> =
  T extends `${string}${infer Unit extends '%'}`
      ? Unit
      : '';

type PercentageParser<T extends string> = [
  ParseSign<T>,
  ParseNumber<T>,
  ParsePersent<T>
];

• 解析正负号：

  • ParseSign<T>：检查字符串T是否以+或-开头

    • 如果T以+或-开头，则推断出正负号Sign

    • 否则，返回空字符串

• 解析数字：

  • ParseNumber<T>：从字符串T中提取数字部分

    • 使用ParseSign<T>和ParsePersent<T>辅助解析正负号和单位

    • 如果T可以表示为${ParseSign<T>}${infer Number}${ParsePersent<T>}，则推断出数字部分Number

    • 否则，返回空字符串

• 解析单位：

  • ParsePersent<T>：检查字符串T是否以%结尾

    • 如果T以%结尾，则推断出单位Unit

    • 否则，返回空字符串

• 组合结果：

  • 将解析的正负号、数字和单位组合成一个数组，返回[ParseSign<T>, ParseNumber<T>, ParsePersent<T>]