On Fri Feb 7 12:14 PM, Tab Atkins Jr. wrote:
> >
> > From a user perspective, can someone explain what chain() does?
>
> .chain returns what is directly inside the promise, without doing any
> additional
> magic. This is different from .then, which "flattens"
> promises.
>
> For a more concrete example, assume that "x" is a Promise<Promise<integer>>.
> That is, it's a promise, holding a promise, holding an integer.
> x.chain(arg=>"arg is
> a Promise<Integer>"), x.then(arg=>"arg is an Integer").
>
Thoughts on adding options/flags to then()?
e.g.
x.chain equivalent to x.then(promise, {unwrap: false});
Promises.all() could be similarly augmented to support serial execution.
The api signatures become ~
Promise.prototype.then ( onFulfilled , onRejected|PromiseOptions ,
PromiseOptions )
Promise.all ( iterable , PromiseIterateOptions )
Defaults:
PromiseOptions = {
unwrap: true
}
PromiseIterateOptions extends PromiseOptions {
serial: false
}
Don't have convincing use case but can pass options to then() during iteration:
Promises.all([a,b,c], {unwrap: false});
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