How to download file from picker without node.js?

When using the Dropbox Chooser, it will return the link to each selected file in the "link" field of the returned object for each file.

I see you're using "linkType" of "preview" here. If you just want to download the selected file data, you should use a "linkType" of "direct" instead. That will make the returned "link" a temporary direct link, which you can access directly to get the file data, without using the Dropbox API. That is, you can issue a standard HTTP GET request (either client-side in the browser, or server-side from your server) to retrieve the linked file data.