I think you are confusing the internal spec function from the API function deliverChangeRecords.
Object.deliverChangeRecords always returns undefined. It is the internal [[DeliverChangeRecords]] that gets called until the queue of change records is exhausted. The point of Object.deliverChangeRecords is to get a synchronous delivery to the function that is listening to the mutations. http://jsbin.com/qazipicipume/1/edit?js,console HTH On Tue, Sep 9, 2014 at 9:50 PM, Jeremy Darling <[email protected]> wrote: > I maintain a Shim of Object.observe ( > https://github.com/jdarling/Object.observe) that has been gaining in > popularity since Chrome implemented the functionality in their public > release. It had some usage before but it has really started picking up > since. > > That being beside the point, someone asked us about implementing the > update to deliverChangeRecords ( > https://github.com/jdarling/Object.observe/issues/13). It seems that at > some time deliverChangeRecords moved from the ObjectNotifier to Object > itself. > > Per the spec at > http://wiki.ecmascript.org/doku.php?id=harmony:observe_public_api > > Object.deliverChangeRecords > > A new function Object.deliverChangeRecords(callback) is added, which > behaves as follows: > > 1. If IsCallable(*callback*) is not *true*, throw a TypeError > exception. > 2. Call [[DeliverChangeRecords]] with arguments: *callback* repeatedly > until it returns false (no records were pending for delivery and callback > no invoked). > 3. Return. > > > This seems very grey and not well defined at all. One would assume that > per the above the following code would function calling changeHandler2 for > all change records (and maybe, its unclear from the above, changeHandler1 > as well). > > > var obj = {}; > var changeHandler1 = function(changes) { > console.log('1)', changes); > }; > > var changeHandler2 = function(changes) { > console.log('2)', changes); > }; > > Object.observe(obj, changeHandler); > obj.test = 5; > > while(Object.deliverChangeRecords(changeHandler2)){ > console.log('got a change') > } > > So we went to Chrome 36 and looked at how it handled the above code. To > our surprise changeHandler1 got called with the change but changeHandler2 > did not get called, also 'got a change' was never logged to the console. > > This lead us to assume that the handler must be one that was already > registered with Object.observe. So we tried the following code instead: > > var obj = {}; > var changeHandler = function(changes) { > console.log('1)', changes); > }; > > Object.observe(obj, changeHandler); > obj.test = 5; > > while(Object.deliverChangeRecords(changeHandler)){ > console.log('got a change') > } > > When running the above changeHandler seems to be called via the normal > Object.observe pipe and still 'got a change' is not recorded in the > console. Basically making Object.deliverChangeRecords appear to be a noop > that actually ignores the callback that has been passed into it. > > So, after all the above, here is my question; What exactly is > Object.deliverChangeRecords supposed to do? As a follow on to that, can > someone post a test scenario that actually covers its proposed actions so > we can implement it? > > Seems to me, to add it in the way Chrome as so far we could just noop it > and go on, but that just doesn't feel right in the grand scheme of things. > > Thanks, > - Jeremy > > > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > > -- erik
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