typescript building a better enum

typescript-better-enum.ts

// https://github.com/krzkaczor/ts-essentials
import { Opaque } from 'ts-essentials';

export const DIRECTIONS = {
  UP: 'Up' as Opaque<'Up', 'DIRECTIONS'>,
  DOWN: 'Down' as Opaque<'Down', 'DIRECTIONS'>,
} as const;
 
export type DIRECTIONS = typeof DIRECTIONS[keyof typeof DIRECTIONS];

// these are valid usages
const d1: DIRECTIONS = DIRECTIONS.UP; 
const d2: DIRECTIONS = "Up" as DIRECTIONS; 
    
// these cause compile errors
// @ts-expect-error
const d3: DIRECTIONS = "Up";
// @ts-expect-error
const d4: DIRECTIONS = "PLASTICS";
    
    
/*
    
const d5: DIRECTIONS =  // Autocompletes: DIRECTIONS.UP, DIRECTIONS.DOWN
    
This is a little more complex than https://medium.com/@maxheiber/alternatives-to-typescript-enums-50e4c16600b1

but it fixes the TS autocomplete concern

compiles as (ES6+; earlier gets var instead of const):

export const DIRECTIONS = {
    UP: 'Up',
    DOWN: 'Down',
};
// these are valid usages
const d1 = DIRECTIONS.UP;
const d2 = "Up";
// @ts-expect-error
const d3 = "Up";
// @ts-expect-error
const d4 = "PLASTICS";

*/