Linking many files best practice

On any project of scale, multiple files are the way to go to keep your sanity. When you have 1500 lines of javascript, and you need to add "one thing" to happen at that "one time", it's very difficult to find, and very easy to screw up.

If your javascript is broken out into 15-20 modules about 80-100 lines of code, it's easier to narrow in and where you need to be working, and its easier to not screw up, since you isolated your changes to only the code that is in that file, not anything else, by accident. Let the computer turn all of those files into one big one.

And in regards to "this advice might change in the future". Well, the performance problem we're trying to avoid here with HTTP 1.1 is latency. Latency is the amount of time it takes to make a response, and receive a response. Less responses to make, less latency, faster page loading. Basically a new TCP connection is used every time it has to fetch an asset from the server. The number of connections are limited by the browser, and the physical distance from the server causes delays, and there is more time delays establishing the connection.

This is why everyone recommends fewer, larger files.

Why is this changing, well, because we HTTP/2 coming. With HTTP/2, numerous assets can be fetched with the same TCP connection, (meaning we reused existing connections).

Check this out from New Relic: https://blog.newrelic.com/2016/02/09/http2-best-practices-web-performance/

The article is only from Feb 9th, so it's relatively new...but it sounds like this is the direction we are heading.