Comment #30 on issue 3093 by dome...@domenicdenicola.com: Debugging promises
http://code.google.com/p/v8/issues/detail?id=3093
Jake: what libraries like Bluebird do is wait until the end of the turn to
make any decisions about unhandled or not. So in your particular examples:
var p = new Promise(function(resolve, reject) { reject(new
Error('Something went wrong'); });
p.then(function(result) {
console.log('Promise success', result);
}, function(error) {
console.error('Promise failed', error);
});
Handled, since by the end of the turn an error handler is attached (and the
return value of p.then is fulfilled).
var p = Promise.resolve();
var q = p.then(function onFulfilled() {
var r = Promise.reject();
return r;
});
Handled, since during the turn (a) p is fulfilled and so a microtask is
queued to run onFulfilled; (b) onFulfilled runs and creates r, which is
for-now unhandled; (c) onFulfilled returns, and the algorithm that called
onFulfilled takes over, queueing a microtask to run r.then(resolveQ,
rejectQ); (d) said microtask happens, making r now handled, and resolving
q; (e) turn finally ends, and in we survey and find that p is fulfilled, q
is fulfilled, and r is rejected but handled.
Promise.reject().catch(function(){})
Same as the first case, but with less typing.
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