兑现承诺

Question

What's the most kosher way of getting the desired result WITHOUT nesting both promised within a new promise and calling resolve/reject?

Example

const transferFile = (fileName, bucketName)=>{
    const destinationBucket = gcs.bucket(bucketName);
    return exists =  destinationBucket.file(fileName).exists()
        .then(exists=>{
            if(exists[0]){
                return true;
            } else {

                // calling another method that returns a promise

                return file.move(destinationBucket)
                    .then(yay=>{

                        // return yay

                        return yay;
                    });

            }
        });

}

transferFile(image, 'bucketName')
    .then(exists=>{
        console.log(exists);
        transferFile(video, 'bucketName');
    })

    // getting undefined rather than yay

    .then(yay)...

I wish to return the yay value from file.move to the base promise chain. Currently no thrown errors from file.move will be caught in the base promise chain, nor is the value of yay being passed.

Answer 1

transferFile returns the promise, but you discard it in the second call.

So notice that I return it within the then function.

transferFile(image, 'bucketName')
    .then(exists=>{
        console.log(exists);
        return transferFile(video, 'bucketName');
    })

    // getting undefined rather than yay

    .then(yay)...