How to upload an image to s3 in Node

Posting a file from my react front end to the node back end.

request
.post('/api/upload')
.field('fileName', res.body.text)
.field('filePath', `/${this.s3DirName}`) // set dynamically
.attach('file', data.file)
.end((err2, res2) => {
    if (err2){ 
        console.log('err2', err2);
        this.setState({ error: true, sending: false, success: true });
    }else{
        console.log('res2', res2);
        this.setState({ error: false, sending: false, success: true });
    }

});

and then on my node backend I want to upload to s3. I am using busboy to be able to get the multipart file that is posted and then the aws sdk to send to my s3 bucket.

var AWS = require('aws-sdk');

const s3 = new AWS.S3({
  apiVersion: '2006-03-01',
  params: {Bucket: 'bucketName'}
});

static upload(req, res) {

    req.pipe(req.busboy);

    req.busboy.on('file', (fieldname, file, filename) => {
      console.log("Uploading: " + filename);
      console.log("file: ", file);

      var params = {
        Bucket: 'bucketName',
        Key: filename,
        Body: file
      };

      s3.putObject(params, function (perr, pres) {
        if (perr) {
          console.log("Error uploading data: ", perr);
          res.send('err')
        } else {
          console.log("Successfully uploaded data to myBucket/myKey");
          res.send('success')
        }
      });

    });

}

But I get error

Error uploading data:  { Error: Cannot determine length of [object Object]

Am I correct in uploading the file object directly or do I need to parse it? Perhaps I should be using uploadFile instead of putObject?

If it helps, this is the output of my console.logs where I log the file and file name

Uploading: 31032017919Chairs.jpg
file:  FileStream {
  _readableState: 
   ReadableState {
     objectMode: false,
     highWaterMark: 16384,
     buffer: BufferList { head: null, tail: null, length: 0 },
     length: 0,
     pipes: null,
     pipesCount: 0,
     flowing: null,
     ended: false,
     endEmitted: false,
     reading: false,
     sync: true,
     needReadable: false,
     emittedReadable: false,
     readableListening: false,
     resumeScheduled: false,
     defaultEncoding: 'utf8',
     ranOut: false,
     awaitDrain: 0,
     readingMore: false,
     decoder: null,
     encoding: null },
  readable: true,
  domain: null,
  _events: { end: [Function] },
  _eventsCount: 1,
  _maxListeners: undefined,
  truncated: false,
  _read: [Function] }

via Stretch0