遍历数组并与Bluebird联接

Question

Is there a better way to write this? For the most part, the code below works, but I would like to clean it up if possible.

For reference, outputs in the initial callback is an array of objects, containing the file path and some metadata. I would like to have access to this metadata when calling this.track.attach() , but I'm unsure how to access it later in the promise chain.

var query  = Track.findById('54d5059b7403dda6395bb08b').exec();
var encode = encoder.encode('/* file path */');

Promise.join(query, encode, function (track, outputs) {
  this.track = track;
  return Promise.map(outputs, function (output) {
    return upload.create(output.path, '/jr' + path.extname(output.path));
  });
}).each(function (output) {
  this.track.attach(output.name, 'media');
}).then(function () {
  return this.track.saveAsync();
}).catch(function (err) {
  console.log(err);
}).finally(function () {
  encoder.cleanup();
}).bind({});

Answer 1

Here's one thing you could do. It avoids the hacky .bind() and this.track :

var query  = Track.findById('54d5059b7403dda6395bb08b').exec();
var encode = encoder.encode('/* file path */');

function createForOutput(output) {
    return upload.create(output.path, '/jr' + path.extname(output.path));
}

function saveToOutputs(track, outputs) {
    return Promise.map(outputs, createForOutput)
    .each(function (output) {
        track.attach(output.name, 'media');
        return track.saveAsync();
    });
}

Promise.join(query, encode, saveToOutputs)
.catch(function (err) {
  console.log(err);
}).finally(function () {
  encoder.cleanup();
});

This approach uses a bit deeper nesting, but I think it may be a little clearer:

var query  = Track.findById('54d5059b7403dda6395bb08b').exec();
var encode = encoder.encode('/* file path */');

function createForOutput(output) {
    return upload.create(output.path, '/jr' + path.extname(output.path));
}

function saveToOutputs(track, outputs) {
    return Promise.each(outputs, function (output) {
        createForOutput(output).then(function () {
            track.attach(output.name, 'media');
            return track.saveAsync();
        });
    });
}

Promise.join(query, encode, saveToOutputs)
.catch(function (err) {
  console.log(err);
}).finally(function () {
  encoder.cleanup();
});