The value of the 'Access-Control-Allow-Origin' header in the response must not be the wildcard '*'

I used an example Meteor app, and in server/main.js I just used the node library normally:

var Dropbox = require('dropbox');

    const dbx = new Dropbox({accessToken: "<ACCESS_TOKEN>"})
    dbx.filesUpload({path: "/test_207235.txt", contents: "some test data"})
      .then(function (response) {
        console.log(response)
      })
      .catch(function (error) {
        console.error(error)
      })

That uploaded the file successfully. Attempting the same in client/main.js failed with the same error you got.

I don't have a more advanced sample available though. The filesUpload method takes a string or buffer, but beyond that I'm afraid I can't offer much insight as to how to manage files/data in node and Meteor themselves.

If you want to upload directly from the user's browser, you can use the JavaScript SDK in the browser's JavaScript. E.g., include the library via a script tag in your HTML, and run JavaScript from a script tag, as shown in the basic browser example.