AWS JS S3: What is the type of 'stream' in ManagedUpload?

Looking at http://ift.tt/1JNNJrM

var upload = new AWS.S3.ManagedUpload({
  params: {Bucket: 'bucket', Key: 'key', Body: stream}
});

Body is suppose to be a stream. How can I create a stream from local file if I want to use this ManagedUpload in a browser?

And is that stream different than streamObject in uploadPart

Body: new Buffer('...') || 'STRING_VALUE' || streamObject,

http://ift.tt/1zfE8io