typescript type for all possible values of enum

Question

So I know that keyof typeof <enum> returns a type of all possible keys of enum, such that given

enum Season{
 WINTER = 'winter',
 SPRING = 'spring',
 SUMMER = 'summer',
 AUTUMN = 'autumn',
}

let x: keyof typeof Season;

is equivalent to

let x: 'WINTER' | 'SPRING' | 'SUMMER' | 'AUTUMN';

my question is how do I get a type that will be equivalent to one of the possible values of the enum, for example:

let x: 'winter' | 'spring' | 'summer' | 'autumn';

The type Season is equal to the union of the enum object's values, although Season is a subtype of 'winter' | 'spring' | 'summer' | 'autumn'. Does Season not work for you? (e.g., declare let s: Season; let x: 'winter' | 'spring' | 'summer' | 'autumn' = s;) — jcalz
– jcalz, Commented Sep 18, 2019 at 19:01
very good explanation provided in this link stackoverflow.com/questions/52393730/… — Siddharth Pal
– Siddharth Pal, Commented Sep 18, 2019 at 19:12
Can you explain why you need access to bare string literal versions of the enum? For example, why not just use let x: Season = Season.WINTER which is essentially the same thing? Even if you could do let x: Magic<Season> = 'winter', what would you do with it? I want to see more of a use case here — jcalz
– jcalz, Commented Sep 18, 2019 at 19:23

Scott Bushman · Accepted Answer · 2023-08-23 17:35:25Z

3

I had the same question. Solved it with this:

    enum Season{
      WINTER = 'winter',
      SPRING = 'spring',
      SUMMER = 'summer',
      AUTUMN = 'autumn',
    }

    type SeasonEnumValues = `${Season}`;

SeasonEnumValues is equivalent to the following:

    type SeasonEnumValues = 'winter' | 'spring' | 'summer' | 'autumn'

answered Aug 23, 2023 at 17:35

Scott Bushman

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Siddharth Pal · Accepted Answer · 2019-09-18 19:08:49Z

2

Typescript doesn't allow this but as a workaround, we can make it with an object whose property values are string literals:

  const createLiteral = <V extends keyof any>(v: V) => v;
  const Season = {
   WINTER: createLiteral("winter"),
   SPRING: createLiteral("spring"),
   SUMMER: createLiteral("summer")
  }
  type Season = (typeof Season)[keyof typeof Season]
  const w: Season = "winter"; // works
  const x: Season = "sghjsghj"; // error

Hope this helps!!! Cheers!

answered Sep 18, 2019 at 19:08

Siddharth Pal

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1 Comment

f.khantsis Over a year ago

thanks, but the enum definition comes from an external library

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