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Comment by zdragnar | Hacker News Reader

Enums aren't simply strings, though they can be reified as such in JS if you assign string values to them. It's more appropriate to think of them as symbols (from a type perspective)- seeing `Direction.North` is a whole lot more semantically meaningful than the string "north" in code.

More than that, refactoring tooling Just Works with enums. On the other hand, if you're passing strings around everywhere and attempt to refactor a type that is a union of strings, there's plenty of cases where refactoring tooling can't help you, and you get to manually clean up the errors.

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> seeing `Direction.North` is a whole lot more semantically meaningful than the string "north" in code

This is subjective, so we can agree to disagree, but personally assuming I have typechecking/autocomplete I really prefer knowing exactly what I have (a string), and not hiding it behind an abstraction

And, if you ever just want the values enumerated for whatever reason, you can always do it yourself explicitly:

  const Direction = {
    North: 'North',
    South: 'South',
    East: 'East',
    West: 'West'
  } as const

  type Direction = keyof typeof Direction

Compared with the above, the special enum syntax just creates unnecessary magic in my opinion; it even breaks TypeScript's rule of not having any runtime footprint

> More than that, refactoring tooling Just Works with enums

I just entered the following in my editor:

  type MyEnum = 'A' | 'B' | 'C'
  const x: MyEnum = 'A'

1. When I typed open-quote in front of `=`, it intellisensed/autocompleted on the possible strings

2. I was able to right-click 'A' in the type definition, click "Rename...", and then it updated both the type and the 'A' literal value with the new value

Now try this:

    type MyEnum = 'a' | 'b' | 'c';

    function test(val: MyEnum) {
      return val;
    }

    // refactors
    test('a');

    // does not refactor
    const testVal = 'a';
    test(testVal);

The simple fact is that- as far as the type system is concerned, enums are more than simple strings, and they are useful for those differences.

As for the readability, it gets a little more interesting when you are interacting with libraries or APIs outside of your control; you end up with hyphenated things, underscored, and other oddities that may not be a one-to-one match between a logical, easily readable key and the underlying value it represents.

> Now try this

Sure- the auto-refactor won't work here, only the typecheck, and that's the desired behavior in this case because the intended use of 'a' is not necessarily known at that point in the code. Which is the point you're making I guess, though I have to say, in practice this is an unusual case that I never really see; usually if I'm creating an enum-string it's directly in a function call, typed object literal, etc.

> as far as the type system is concerned, enums are more than simple strings

  enum MyEnum {
      Foo,
      Bar
  }

  function test(val: MyEnum) {
      return val;
  }

  test(MyEnum.Foo)
  test('Foo')

I was surprised to find you were right about this; I expected the above to pass checks, but it doesn't. TypeScript actually does treat the enum as more than just its underlying value. So that's interesting- and that's the first reason I've really seen to use these

But I think I still prefer plain values, for myself. There's just something that feels right and pure about using plain JSON-like JavaScript values, and then overlaying types on top of them that have no effect on their behavior and don't obscure their underlying representation. You know exactly what you've got, it's maximally duck-typeable, it's unchanged when it gets (de)serialized, it all just feels better to me

>though I have to say, in practice this is an unusual case that I never really see

They happen once in a blue moon and when they do, you hate your life for a day. Maybe a week.

Plain values also have the problem of losing context. This primarily hits those who don't know the code. That's the whole selling point of OOB and related abstractions, anyway.

Both of the above happening in tandem isn't that rare and a realistic risk factor for big projects.

> you hate your life for a day. Maybe a week.

I'm not sure why I would? TypeScript would still lead me straight to the problem via type incompatibilities; it just wouldn't perform the fix for me automatically in this one specific case

What do you mean with "does not refractor"?

Do you mean it doesn't compile, because it doesn't. You need to write either

    const testVal: MyEnum = "a"

    const testVal = "a" as MyEnum

The latter passes typechecking with invalid values, both change automatically for me if I refractor the symbol values in VS Code.

It checks fine for me.

    const testVal = "a"

Here, TypeScript infers that it is of type "string", and knows the value, so it is perfectly happy accepting it to ALSO be of type MyEnum. This is the problem- refactoring MyEnum means that testVal is not automatically updated, because the type is really "string" that just-so-happened to duck-type into MyEnum at the function call site.

On the other hand, if MyEnum were actually an enum rather than a union of strings, this problem wouldn't have happened.

If you don't want enum's runtime footprint, just use `const enum`

Less typing and easier to read than your solution

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