typescript enums without using enum

identity_enum.ts

type EnumKey<EnumType> = keyof EnumType;

type IdentityEnum<T> = T extends Array<infer E extends string> ? { 
    readonly [P in T[keyof T] as E]: E
} : never;

type IdentityEnumConstructor = {
    <T extends string[]>(...values: T): IdentityEnum<T>;
    new <T extends string[]>(...values: T): IdentityEnum<T>;
};

type EnumField<T> = T extends IdentityEnum<string[]> 
    ? keyof T : T extends string 
    ? T : never;

const IdentityEnum = function<T extends string[]>(...names: T) {
    const obj: Partial<IdentityEnum<T>> = {};
    for (const name of names) {
        (obj as any)[name] = name;
    }
    return {...obj} as const;
} as IdentityEnumConstructor;

Example

// We construct a new enum and a type to be able to reference an enum field
const Language = IdentityEnum('English', 'German', 'Italian');
type Language = EnumField<typeof Language>;

// Some random object that has our enum keys as property keys
const abbreviations: Record<Language, string> = {
    [Language['English']]: 'EN',
    [Language['German']]: 'GER',
    [Language['Italian']]: 'ITA',
    // or
    'English': 'EN',
    'German': 'GER',
    'Italian': 'ITA',
};

console.log(Language['German']);    
// [LOG]: German

console.log(abbreviations[Language['German']]);
// [LOG]: GER
console.log(abbreviations['German']);
// [LOG]: GER

Example on typescript playground