The enum is an original syntax of TypeScript (it does not exist in JavaScript). So it is converted to like the following form as a result of transpilation:
let OperatingSystem;
(function (OperatingSystem) {
OperatingSystem[OperatingSystem["MacOS"] = 0] = "MacOS";
OperatingSystem[OperatingSystem["Windows"] = 1] = "Windows";
OperatingSystem[OperatingSystem["Linux"] = 2] = "Linux";
})(OperatingSystem || (OperatingSystem = {}));
In this question, the type should convert a given string tuple to an object that behaves like an enum. Moreover, the property of an enum is preferably a pascal case.
Enum<["macOS", "Windows", "Linux"]>
// -> { readonly MacOS: "macOS", readonly Windows: "Windows", readonly Linux: "Linux" }
If true is given in the second argument, the value should be a number literal.
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
}
>>,
]