Allen Wirfs-Brock wrote:
Another loose end.
With the addition of for-of, for-in reverts back to always iterating
over the property keys of an object as it does not support the
generalized iteration protocols. An implication of this is that using
a de-structuring pattern as the iteration variable has very limited
utility:
for (let [c] in obj) print(c); //print the first character of
each of obj's enumerable property names
for (const {length:len} in obj) print(len); print the length
of each of obj's enumerable property names
Given this lack of utility, why should we allow de-structuring in this
context?
These are not totally silly examples. I say when in doubt, let language
regularity win.
We are also thereby future-friendly in case some evolution of property
keys becomes even more structured. I know, unlikely, but again:
regularity when in doubt.
Eliminating it arguably increases language complexity by
introducing in a bit more grammar irregularity. On the other hand,
eliminating useless functionality can be seen as as simplification.
Not useless, your own examples show use-cases.
I'm leaning towards banning destructing in for-in.
Too nannyish!
/be
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