Description

Typescript supports enum now, but there are times when you may want a little more flexibility than built-in enums give you; this package was adapted from an example in a gist linked from a typescript issue which I cannot now find, but suffice it to say that though we have modified it a bit the idea is not original to us.

Installing

npm install --save @gradecam/tsenum

Basic Usage

import {MakeEnum, TypeFromEnum} from 'tsenum';

const Colors = MakeEnum({
    Red: 'red',
    Blue: 'blue',
    Green: 'green',
    Violet: 'violet',
    Black: 'black'
});
type Colors = TypeFromEnum<typeof Colors>;

// type Colors = 'red' | 'blue' | 'green' | 'violet' | 'black'
// value Colors is a frozen object with the keys expected
// typeof Colors.Red is 'red', et al

carColor: Colors = 'red'; // valid
carColor = Colors.Green; // valid
carColor = 'yellow'; // typescript error, not a valid color

Combining types

MakeEnum will merge multiple enum objects into one (up to 9), allowing you to combine types.

import {MakeEnum, TypeFromEnum} from 'tsenum';

const PrimaryColors = MakeEnum({
    Red: 'red',
    Blue: 'blue',
    Green: 'green',
});
type PrimaryColors = TypeFromEnum<typeof PrimaryColors>;

const SecondaryColors = MakeEnum({
    Yellow: 'yellow',
    Cyan: 'cyan',
    Magenta: 'magenta'
});
type SecondaryColors = TypeFromEnum<typeof SecondaryColors>;

const AllColors = MakeEnum(PrimaryColors, SecondaryColors);
type AllColors = TypeFromEnum<typeof AllColors>;
// type AllColors = 'red' | 'blue' | 'green' | 'yellow' | 'cyan' | 'magenta'

Getting an array of possible values

Sometimes you may want an array of possible values, such as when defining an enum type in a mongoose schema. Since the enum is an object, you can use Object.values to get that:

import {MakeEnum, TypeFromEnum} from 'tsenum';

const PrimaryColors = MakeEnum({
    Red: 'red',
    Blue: 'blue',
    Green: 'green',
});
type PrimaryColors = TypeFromEnum<typeof PrimaryColors>;

const PrimaryColorList = Object.values(PrimaryColors); // ['red', 'blue', 'green']
// typeof PrimaryColorList = Array<'red'|'blue'|'green'>