Hey! So, you’re serving /index.js. Our guide (the one I think you’re referencing) asks you to ensure that you’re serving /index.html.
If I browse to https://vigorous-dijkstra-4c4ca1.netlify.app/index.js, I can see the content. You’ll need to pass this through /index.html 
If you read a guide which did say /index.js, please let me know and I’ll make sure that’s corrected!