[Vuejs]-Why Node.js can't process the request from Vue.js?

In vue, you are doing a post request to /csv, but in your app.js you are defining the /csv route as GET, that is your problem 😀

UPDATE

If you want this to work with the animation download like chrome
Take a look at this link
https://gist.github.com/javilobo8/097c30a233786be52070986d8cdb1743