enum は TypeScript 独自の文法です(JavaScript にはありません)。そのため、以下の形式にトランスパイルされます。
let OperatingSystem
;(function (OperatingSystem) {
OperatingSystem[(OperatingSystem['MacOS'] = 0)] = 'MacOS'
OperatingSystem[(OperatingSystem['Windows'] = 1)] = 'Windows'
OperatingSystem[(OperatingSystem['Linux'] = 2)] = 'Linux'
})(OperatingSystem || (OperatingSystem = {}))
この問題では、文字列のタプルを enum と同じようなオブジェクトに変換する型を実装します。 さらに、enum のプロパティはパスカルケースであることが好ましいです。
Enum<['macOS', 'Windows', 'Linux']>
// -> { readonly MacOS: "macOS", readonly Windows: "Windows", readonly Linux: "Linux" }
第 2 引数にtrueが与えられた場合、値は数値リテラルとなります。
Enum<['macOS', 'Windows', 'Linux'], true>
// -> { readonly MacOS: 0, readonly Windows: 1, readonly Linux: 2 }
import type { Equal, Expect } from '@type-challenges/utils'
const OperatingSystem = ['macOS', 'Windows', 'Linux'] as const
const Command = ['echo', 'grep', 'sed', 'awk', 'cut', 'uniq', 'head', 'tail', 'xargs', 'shift'] as const
type cases = [
Expect<Equal<Enum<[]>, {}>>,
Expect<Equal<
Enum<typeof OperatingSystem>,
{
readonly MacOS: 'macOS'
readonly Windows: 'Windows'
readonly Linux: 'Linux'
}
>>,
Expect<Equal<
Enum<typeof OperatingSystem, true>,
{
readonly MacOS: 0
readonly Windows: 1
readonly Linux: 2
}
>>,
Expect<Equal<
Enum<typeof Command>,
{
readonly Echo: 'echo'
readonly Grep: 'grep'
readonly Sed: 'sed'
readonly Awk: 'awk'
readonly Cut: 'cut'
readonly Uniq: 'uniq'
readonly Head: 'head'
readonly Tail: 'tail'
readonly Xargs: 'xargs'
readonly Shift: 'shift'
}
>>,
Expect<Equal<
Enum<typeof Command, true>,
{
readonly Echo: 0
readonly Grep: 1
readonly Sed: 2
readonly Awk: 3
readonly Cut: 4
readonly Uniq: 5
readonly Head: 6
readonly Tail: 7
readonly Xargs: 8
readonly Shift: 9
}
>>,
]