Express res.sendfile(bundle) just loads browser with plain JS source in the actual window

[myk5000]

Been using this boilerplate for dev using react (its great) and I'm having trouble testing sudo production build.
I'm trying to deploy to heroku by adding express server code and a procfile. I do a webpack -p to create the dist folder with its contents (bundle.js, [hash].jpegs).
I then use then express code to provide a way to serve up my simple react app.

`app.use("/static", express.static(path.join(__dirname,'dist')));
//used for referencing images from the bundle.js in the dist folder

app.get('*', (req, res) => {
res.sendFile(path.resolve(path.join(__dirname,'dist'), "bundle.js"));
});`

The weird thing is that if the 'app.use' line for setting up static reference is commented out, the homepage is rendered in the browser without the images loading simply by returning the bundle.js file from the get request. However if I do leave the app.use line in the code.. the browser just shows raw JS source in the window and does not render the page at all.. This has got me pretty confused, any tips would would be great. Thanks.