On Thu, Sep 22, 2016 at 1:14 PM, Bob Myers <[email protected]> wrote:
> In the proposed "pick/destructure into an object" syntax, I would use
> identical destructuring syntax
>
> ```
> obj.{foo: {bar: {qux}}}
> ```
>
> which would turn into `{qux: obj.foo.bar.qux}`.
>
> We are simply using identical destructuring syntax to destructure into an
> object instead of a variable.
>
I'm sorry, Bob, the link in your original post in this thread has a link to
the proposal; it's perfectly clear on this, and I should have gone back to
it.
OK, I think I understand the proposal now. A few comments:
1. The gist says:
> The syntax of the *Assignment Pattern* is identical.
I don't think this is right; I think you want all the right-hand sides
of all the properties in the tree to match PropertyName. In
AssignmentPattern, those can be any LeftHandSideExpression:
{text: f().q[13].name} = obj;
But that wouldn't make sense in pick notation:
obj.{text: f().q[13].name} // ???
2. I mentioned scoping earlier. What I mean is, in expressions like
obj.{[p]: p}
the two identifiers `p` mean different things (the first `p` is a
variable name, the second `p` a property name), which is new and subtle.
The same thing happens in `obj.{p = p}`, except the other way round.
Destructuring does just a touch of this in the shorthand case, but I never
found that confusing. This is.
3. I wonder if this can be made more symmetrical -- as it stands, it
allows you to flatten a complex object:
// from a tree of 3 objects to one
let rect = corners.{
p0: {x: left, y: top},
p1: {x: right, y: bottom}
};
The reverse would be to add structure to a flat object. There's no way
to do that, right?
// turn the 1 object back into a tree of 3?
let corners = rect.{ ??? };
Likewise, it seems you can turn an array into a plain object, but not
the other way around?
let point = coords.[x, y]; // {x: coords[0], y: coords[1]}
let coords = point.{???}; // [point.x, point.y]
Honestly even the examples that do work seem ugly to me. I think pretty
much all the value in the proposal is in the simplest case,
`obj.{identifier, ...}`.
-j
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