Question

I’m using async and trying to get data to pass back. Is this possible or do I need to use another library approach?

Ideally, I’d like to do something like:

async.forEach(txids, processTransaction, function(asyncErr, outputTotal) {

Answer 1

I think you want async.reduce(), similar to Array.reduce() but asynchronous.

The given example is:

async.reduce([1,2,3], 0, function(memo, item, callback){
    // pointless async:
    process.nextTick(function(){
        callback(null, memo + item)
    });
}, function(err, result){
    // result is now equal to the last value of memo, which is 6
});

You would probably do something similar to:

async.reduce(txids, {}, processTransaction, function(err, output) { });

I’m not sure what processTransaction returns, so I’m not sure what your memo (or initialValue) should be.