Looking through the destructuring proposal
http://wiki.ecmascript.org/doku.php?id=harmony:destructuring
there seems to be no mention of 'as' patterns. In typical pattern
matching constructs (SML, Haskell, ..), 'as' patterns allow to name
a sub-object while continuing the match for its sub-structures.
For instance, with
var obj = { a: 0, b: { x: 1, y: 2} };
something like
let { b: b as {x,y} } = obj
would result in the bindings of b to obj.b, x to obj.b.x, y to obj.b.y.
This avoids needless repetition when both a subobject and its
components need to be extracted. Without 'as', each such case
leads to a separate destructuring assignment
let { b } = obj
let { b: {x,y} } = obj
Shouldn't 'as' patterns be included in destructuring? Or have I
missed an equivalent feature?
Claus
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