How to wrap callback-function to get promise in WinJS?

Question

I wonder how I can achieve a conversion such as:

fn(args, function (errors, results) {})

to

fn(args).then(function (results){})

by simply calling something like

makePromise(fn, args).then(function (results))

in WinJS.

Background: I have a predefined interface using async callbacks, but I'd like to use them as a promise.

Is this possible in this way? Maybe even directly supported by WinJS?

Answer 1

No, I could not find such a method in the official docs. However, this should do it:

function makePromise(fn, args) {
    return new WinJS.Promise(function init(completeDispatch, errorDispatch) {
        fn(args, function handler(errors, results) {
            if (errors)
                errorDispatch(errors);
            else
                completeDispatch(results);
         });
    });
}