When you develop an app, performance is a vital concern. Every software developer needs to monitor as well as improve performance in each layer of the app. Starting from the database till server-side language, you will find many chances to arise performance issues and remember that the front end is not an exception.
Turn to HTTP/2: You need to make use of HTTP/2 and not HTTP/1.1. It makes use of multiplexing and it means that several requests are simultaneously sent. HTTP/1.1 needed that each of the requests gets finished before the next one is started. This as well as other improvements in the HTTP version will be improving the performance of the site.