download file API JS

Hi there,

I am developing a thiny web client for Dropbox using the Javascript API. What I want to have is the basic functionality (upload, download, and delete files) from an account.
I am having trouble with the downloadFile function which I don't really understand and doesn't work as I expected. I have to say that I am learning JS, and sorry, but not found so much documentation about that. I've read the API documentation. 

This is my code:

		function downloadFile(){
			var itemValue = obtenerItemValue();
			
			if (itemValue == null)
				alert('Hay que seleccionar antes un archivo');
			else{
				alert('Archivo a descargar: ' + itemValue);

				dbx.filesDownload({path: '/' + itemValue})
				
					.then(function(response) {
					})
					.catch(function(err) {
					console.log(err);
					callback('Error downloading file using the Dropbox API');
					});
				
				recargarItems();
			}
		}

And I don't know what to do, the action send a POST message and gets back a response in application/byte type, as shown here:

Anyone could help me please?
Thanks