10 
enum SomeEnum {
  a = 10
  b = 20
}

const n: number = 20;

const enumValue: SomeEnum = ???;

Is there a way to convert n to enumValue without having to write a switch-case for every enum-type.

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Yes, there is a way:

enum SomeEnum {
  a = 10,
  b = 20
}

const n: number = 20;

const enumValue: SomeEnum = 20; // ok

const enumValue: SomeEnum = 21; // ok, please keep in mind it is unsafe

I encourage you to not do it.

Like @Beraliv mentioned in their comment, since TS 5.0 All enums Are Union enums, there is an error if you want to assign invalid number:

const enumValue: SomeEnum = 21;

If you can't switch to the newest version of TypeScript, you can check my article about safer enums and my answer

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3 Comments

You can also validate the number by indexing it through the enum type twice: const enumValue: SomeEnum | undefined = SomeEnum[SomeEnum[n] as keyof typeof SomeEnum]
@E_net4theflagger nice approach!
It's no longer possible to assign it in TypeScript 5.0 (which is in beta now) – tsplay.dev/Wzaz4m