Options for Parsing Excel Files in ExtJS

Options for Parsing Excel Files in ExtJS

I'm having a very hard time accomplishing my main goal: extracting data
from an xlsx excel file
I'm running ExtJS + node.js, and I see two options:
Use this XLSX.js framework to convert the base64 string into js
object-representations of xlsx worksheets for me to use. Problem is, I
have no idea how to get a base64 string from an xlsx file..
Upload the xlsx file to the server, do the conversions there using
node-xlsx, the send the object-representations back ala json. Having lots
of difficulties here since ExtJS doesn't use real AJAX for file uploads so
I don't know how to send the results back..
Has anyone had experience with this or could advise a solution? Having
lots of trouble..