This is a quick one to share which I won't explain here how it works as the code below has comments within it. In short it allows it create a HTML table from an XLSX dataset without the need to upload the file first to your server.
All you need to do is open your XLSX document, "Select All", "copy" the data, come to the HTML page below, put focus on the <textarea> box, and "paste" the text in. In some instance (large data sets) this might take a couple of seconds.
Due to restriction in Chrome and Firefox you cannot access the Clipboard so the only little hurdle which I don't like is that you need to paste the data in to a textarea.