The ability to both name and de-structure an argument.
Relying on the spread operator does not archive the same effect considering
that the spread operator "by design" has some short-comings related to
exotic objects when the objects in question have a rich prototype you want
to preserve.
Consider the following proposal:
function fn (arg pick {a, b = arg.b = 'value'}) {}
This would allow four fundamental things of note missing from current
de-structuring status-quo:
1. The ability to have both named arguments and de-structuring.
2. The ability to reference the named argument within the de-structure.
This allows the above pattern of setting a default value on the passed
argument when it doesn't exist.
3. This in turn also affords you the ability to de-structure while also
preserving the exotic nature of an object when it is not a POJO object.
That is when "arg" is an exotic use-defined object using the spread
operator "{...arg}" will discard its prototype.
For example:
function a ({a, ...b}) { return b }
a([1, 2])
Returns a object with index-able keys instead of the array.
4. Consequently this addition would also afford the avoidance of any
overhead that one might want to avoid with the rest spread operation: {a,
b, ...arg} in hot paths.
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