Phoenix 1.4 has been released and uses Webpack etc for managing assets instead of Brunch.
1) put your js files in the directory: assets/static
2) add the file names to the Plug.static section in the file: endpoint.ex
plug Plug.Static, at: "/", from: :myapp, gzip: false, only: ~w(css fonts images js favicon.ico robots.txt jquery.min.js vuedist.js)
3) import your js file in the templates/layout/app.html.eex.
That should be it.
On a related note, the article below takes a look at why your node_modules directory is so ridiculously large “out of the box”.