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Comment by manigandham | Hacker News Reader

The topic is that all code is text, and everything can be parsed and understood based on specific language grammars, even if they're embedded within each other.

What are you even arguing at this point? This isn't about compilation or strings anymore. You don't like Vue's specific DSL? Or you don't understand it? Or you found a problem with the documentation? Or do you need a full grammar and syntax definition before you can do anything?

It's basically any valid `for..in/of` expression but you can always solve your mystery of "who knows" by just looking at the source code: https://github.com/vuejs/vue-next/blob/master/packages/compi...

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> What are you even arguing at this point?

That Vue isn't "the same as text between script tags". Because "text between script tags" is fully specified, and known to the browser.

Vue's ad-hoc mish-mash of DSLs has to go through an unspecified series of transformations before it can even become a "text between script tags". And that's the issue not just with Vue, but with any other templating layers.

> but you can always solve your mystery of "who knows" by just looking at the source code

Ah yes. The good old "code is the source of truth" fallacy. Can you point to me where exactly in code it specifies this: `Expects: Array | Object | number | string | Iterable (since 2.6)`?

Yes, Vue directives aren't JS. It's a separate DSL. The whole point is that it is a syntax that can be parsed, compiled and understood rather than just "strings".

I'm not sure why you're stuck on this. Templates are just a more simplistic programming language. That's how so many IDEs can still provide help with them.

> It's basically any valid `for..in/of` expression

This isn't true at all though, because `for x in y` is invalid JS.

How is it invalid? Here's the syntax about a for..in loop: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

   for (variable in object) {
     statement
   }

The only difference in Vue is not having to explicitly declare the variable. But so what?

You said "strings are magic and not code" to which I said "all code is text so there are no magic strings". Now you and the other poster keep saying "well this string isn't the same syntax as JS" but I don't see what the point is. Why does it have to be valid JS?

Again, you can embed syntax within each other just fine. JSX has HTML tags inside JS. HTML has tags like <style> and <script> for other languages (regardless of what the default language is or what parses it).

So, for the last time, what's the actual argument?

Because that loop doesn't do what you think it does?

for...in iterates over the keys of an object, but for in in vue iterates over the elements of an array.

Actually, for ... in does both.

It is you who doesn't think that loop does what it actually does.

Please read the spec and verify with your favorite JS runtime before continuing this argument.

    for (x in [6,1,6,2,6,3]) {
      console.log(x);
    }

Please run this in your browser console and tell me if it iterates over the elements of the array.

It does exactly what I think it does, which is either iterate over the properties if it's an object or the elements if it's an array. This is true for Vue and Javascript. I suggest you read the documentation I linked earlier.

Also Vue's directives are not JS. It's a separate DSL. I've repeated this enough so I'll end this discussion here.

> This is true for Vue and Javascript.

This is not true for javascript at all.

    for (x in [6,1,6,2,6,3]) {
        console.log(x);
    }

Please run this in any javascript runtime.

In Javascript, `for..in` prints the keys. In an object, the keys are the properties. In an array, the keys are the indexes. If you want the values then use the key to lookup the value from the object or array.

Either way it's entirely consistent: an iterator that works on both objects and arrays and prints the keys without guaranteeing order. Does that clear up the confusion?

> How is it invalid? Here's the syntax about a for..in loop

   for (variable in object) {
     statement
   }

And here's the syntax for Vue's for..in loop. Only one of it is somewhat Javascript:

   item in items
   (item, index) in items
   (val, key) in object
   (val, name, index) in object

And, of course, there's an extension to that

   v-for="item in items" :key="item.id"

Edit: additionally, from that very link: "for...in should not be used to iterate over an Array where the index order is important." But this doesn't concern Vue, it maintains the order in its for..in.

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