How to use filesDownloadZip() to download zip file in javascript SDK

If you want to get a zip of a folder on Dropbox, the 'filesDownloadZip' method you already found is the right method. (If you only wanted a single file, you would use the 'filesDownload' method.

In either case, when performing a download call like this in Node, if the call succeeds the resulting data is in the 'fileBinary' field. (If running in browser JavaScript, it would be in the 'fileBlob' field.)

In the case of using 'filesDownloadZip', that data is the actual raw data for the zip file containing the requested folder. 

It looks like you have the Dropbox part of this itself working, so I don't think I can offer to much help with the part that you're currently stuck on. Exactly what you do with that returned data and how you serve it back to the user is up to and will depend on the web framework you're using in this case.

That said, I wouldn't expect to use '.json()' or 'JSON.stringify' on the returned data, as it's not an object you necessarilly want to convert into a JSON string. Also, 'window.open' doesn't seem right as that would expect a URL, but the data isn't a URL. 

You should look into how to send a Buffer from your Node backend to the client. For example, here's a question on StackOverflow that looks similar: https://stackoverflow.com/questions/25206141/having-trouble-streaming-response-to-client-using-expressjs