Use object literal as TypeScript enum values

Question

I have an enum:

export enum PizzaSize {   SMALL =  0,   MEDIUM = 1,   LARGE = 2 } 

But here I'd like to use some pair of values: e.g. SMALL I would like to say that it has a key of 0 and a value of 100. I endeavor to use:

export enum PizzaSize {   SMALL =  { key: 0, value: 100 },   // ... } 

But TypeScript doesn't accept this one. How can I do this?

Answer 1

TypeScript supports numeric or string-based enums only, so you have to emulate object enums with a class (which will allow you to use it as a type in a function declaration):

export class PizzaSize {   static readonly SMALL  = new PizzaSize('SMALL', 'A small pizza');   static readonly MEDIUM = new PizzaSize('MEDIUM', 'A medium pizza');   static readonly LARGE  = new PizzaSize('LARGE', 'A large pizza');    // private to disallow creating other instances of this type   private constructor(private readonly key: string, public readonly value: any) {   }    toString() {     return this.key;   } } 

then you can use the predefined instances to access their value:

const mediumVal = PizzaSize.MEDIUM.value; 

or whatever other property/property type you may want to define in a PizzaSize.

and thanks to the toString() overriding, you will also be able to print the enum name/key implicitly from the object:

console.log(PizzaSize.MEDIUM);  // prints 'MEDIUM' 

Answer 2

Update: find @Javarome's answer below, which is more elegant. I suggest using his way.

If you need to use Type, try adding some code. usage: getPizzSizeSpec(PizzaSize.small).value

enum PizzaSize {     small,     medium,     large } interface PizzaSizeSpec {     key: number,     value: number } function getPizzaSizeSpec(pizzaSize: PizzaSize): PizzaSizeSpec {     switch (pizzaSize) {         case PizzaSize.small:             return {key:0, value: 25};         case PizzaSize.medium:             return {key:0, value: 35};         case PizzaSize.large:             return {key:0, value: 50};     } }