for-of loops, IteratorClose and the rest of the iterations in the spec

Boris Zbarsky bzbarsky at mit.edu
Wed Sep 10 10:37:04 PDT 2014


On 9/10/14, 1:28 PM, Allen Wirfs-Brock wrote:
> Right, or come up with some other way to say: "this loop behaves as if it was implemented using for-of".

Thing is, for my Web IDL use case I don't want _quite_ the behavior of 
for-of.  I want something like this:

1. Let method be the result of CheckIterable(V).
2. ReturnIfAbrupt(method).
3. If IsCallable(method) is false, go off and do something else,
    since V is not iterable.
4. Let iter be GetIterator(V, method).
5. ReturnIfAbrupt(iter).

and then IteratorStep my way through "iter".

An additional complication here is that I'm not using this in a 
situation where the return value of my algorithm is an ES6 completion 
(so the ReturnIfAbrupt bits above there are actually somewhat bunk; they 
should be something like "if method is an abrupt completion, then 
propagate method.[[value]] as an exception" or some such; we need to 
figure out how to make the way DOM/IDL talk about exceptions really 
interface well with the way ES does).  So I'm not quite sure what 
IteratorClose should actually do in my setting, assuming it should be 
called at all.

-Boris


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