How to build a type from enum values in TypeScript?
[@hackape 's solution][1] is great, but I found minimal duplication extending his solution as below:
type ReverseMap<T extends Record<keyof T, any>> = { [V in T[keyof T]]: { [K in keyof T]: T[K] extends V ? K : never; }[keyof T]; } const Map = { 'FOO': "foo" as "foo", 'BAR': "bar" as "bar", } const reverseMap: ReverseMap<typeof Map> = Object.entries(Map).reduce((rMap, [k, v]) => { rMap[v] = k; return rMap; }, {} as any); export type Values = keyof typeof reverseMap; // 'foo' | 'bar';
ReverseMap implementation is well explained [here][2]
[1]: https://stackoverflow.com/a/60768453/5519365 [2]: https://stackoverflow.com/a/55209457/5519365
Update: I found a much simpler solution for ReverseMap
const Obj = {
FOO: 'foo',
BAR: 'bar',
} as const;
type ReverseMap<T> = T[keyof T];
export type Values = ReverseMap<typeof Obj>; // 'foo' | 'bar';
Yes, you can use enum values as keys. And you can use a mapped type like the standard library's Record<K, V>
to prevent repetition:
enum FooKeys {
FOO = 'foo',
BAR = 'bar',
}
// probably all you need, but it's a type alias
type FooType = Record<FooKeys, string>;
// if you need an interface instead you can do this
interface FooInterface extends FooType {};
And you can verify that it works:
declare const foo: FooInterface;
foo.foo; // okay
foo[FooKeys.FOO]; // okay
foo.bar; // okay
foo[FooKeys.BAR]; // okay
foo.baz; // error
Does that work for you? Good luck!