Use a UInt8Array with createClassifier

createClassifierByteArray.js

var VisualRecognitionV3 = require('watson-developer-cloud/visual-recognition/v3');
var toBuffer = require('typedarray-to-buffer')

var visualRecognition = new VisualRecognitionV3({
  api_key: 'INSERT YOUR API KEY HERE',
  version: '2016-05-20'
});

var catClassImages = toBuffer(<YOUR_BYTE_ARRAY>);
var dogClassImages = toBuffer(<YOUR_BYTE_ARRAY>);

var params = {
  cat_positive_examples: catClassImages,
  negative_examples: dogClassImages,
  name: 'my-cat-classifier'
};

visualRecognition.createClassifier(params, function(err, res) {
  if (err) {
    console.log(err);
  } else {
    console.log(JSON.stringify(res, null, 2));
  }
});