Node node-csv-parse gives "has no method 'join'" error

Can't seem to get the pipe function working properly as I am getting a "TypeError: Object # has no method 'join'" error. My input file is a very basic comma delimitated csv, nothing too fancy.

I'd like to pipe the output directly to my response.

var output = [];
var parser = parse({auto_parse: true, columns: true});
var input = fs.createReadStream('./uploads/' + req.body.file);
var transformer = transform(function (record, callback) {
    setTimeout(function () {
        callback(null, record.join(' ') + '\n');
    }, 500);
}, {parallel: 10});

transformer.on('error', function (err) {
    res.send(500,err);
    console.log(output);
});
transformer.on('finish', function () {
    console.log('finish');
    console.log(output);
});

input.pipe(parser).pipe(transformer).pipe(process.stdout);