Is it possible to wrap promise inside generator?

Question

I'm trying to create a promise-wrapper using generator so that I can do:

var asyncResult = PromiseWrapper( $.ajax( ... ) );

So far, I've been trying with:

function PromiseWrapper(promise){
    return function *wrapper(promise){
        promise.then(function(result){
            yield result;
        }, function(err){
            throw err;
        });
    }(promise).next().value
}

but this fails because yielding inside a normal is not allowed. Is there any work-around for this? Thank you :D

ps: I'm using babel to translate the code from es6 to es5

Answer 1

It is utterly impossible to wrap a promise in a generator that synchronously yields the promise's result, because promises are always asynchronous. There is no workaround for that, unless you throw mightier weapons like fibers at the asynchrony.

Answer 2

Would this approach work for you http://davidwalsh.name/async-generators ?

A modified example from the link:

function wrap(promise) {
    promise.then(function(result){
        it.next( result );
    }, function(err){
        throw err;
    });
}

function *main() {
    var result1 = yield wrap( $.ajax( ... ) );
    var data = JSON.parse( result1 );
}

var it = main();
it.next(); // get it all started

You should probably read the entirety of that post, the runGenerator is a pretty neat approach.