Generating a Typescript type based on Enum values

Is there a more efficient way to generate a Typescript type based on ENUM values? Currently, I find myself manually creating the type and ensuring it stays synchronized with the ENUM.

Can a type be automatically generated from ENUM values in such a way that any updates to the ENUM are dynamically reflected in the type definition?

enum COLORS {
    RED = 'red',
    BLUE = 'blue',
    GREEN = 'green',
}

// type Colors = COLORS;
type Colors = 'red' | 'blue' | 'green';

// Test case 1
const color: Colors = COLORS.RED;

// Test case 2
const color2: Colors = 'red';

The defined type should seamlessly integrate into these scenarios:

const color: Colors = COLORS.RED;

const color2: Colors = 'red';

Answer №1

I would suggest avoiding the use of enum unless the values are truly opaque, meaning there is no need for any TypeScript code outside the enum declaration to reference the numeric or string values as literals. Personally, I tend to steer clear of numeric enums altogether, as all number values can be assigned to them, which can lead to issues like those mentioned in microsoft/TypeScript#17734.

In the specific scenarios outlined in your example, I would recommend abandoning the use of enum and opting for a strongly-typed enum-like object instead:

const FRUITS = {
  APPLE: 'apple',
  PEAR: 'pear',
  ORANGE: 'orange',
} as const;

This approach allows you to define Fruits programmatically:

type Fruits = typeof FRUITS[keyof typeof FRUITS];

With this setup, everything in your example will still function as intended:

const fruit: Fruits = FRUITS.APPLE;
const fruit2: Fruits = 'apple';

Check out the code in the Playground

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