Looks nice. I love how dedicated typescript is to sticking to standard javascript, even by championing features through the ecmascript standards track.
They understand very well how bad it would be if the two languages were to diverge.
They understand very well how bad it would be if the two languages were to diverge.
type Direction = "up" | "down";Enums are transpired to objects so you can iterate the keys/values. You can't do that with SL which are a transpiler feature only.
Also you can't codedoc string literal values like you can with enums where it shows up with intellisense.
I tend to prefer enums as a result
const types = ['x', 'y', 'z'] as const;
const a: typeof types[number] = 'a'; // not ok
const b: typeof types[number] = 'z'; // ok const enum Directions { Up, Down, Left, Right }
console.log(Directions.Left)
// emits js file with console.log(2)
By using only union types as "enums" and never using enums or namespaces, I guarantee that all the TS-specific code I write can be erased and if I ever were to use just JavaScript in the future, I could.
Also, I use Babel to transpile TS to ES3.
const test(direction: Direction) => direction;
test('up' as 'up');
I wonder if you've seen this quirk of typescript before.
It's when you do
const dir = "up"; // TS infers type "string"
test(dir); // error
They recently added a feature to make this less painful:
const dir = "up" as const;
test(dir); // works
(example in typescript playground: https://www.typescriptlang.org/play/#code/C4TwDgpgBAIglgJwgY...)