Suppose I have 3 js files, how will it affect the load time if I compile it to a single one? Is it wise to do so?
In terms of networking, it will be faster, but not anything significant or measurable. In general, you don't have to worry about how fast plain text files will be downloaded, unless it's especially large. Images and other types of media account for most of the load time on your average web page.
When you program, you should be concentrating on the readability of your code. With how powerful computers and networks have become, making your code readable and easy to follow is more than worth it because you don't have worry about resources, and it will save you so much time if you have/want to update anything later. Unless you are developing for a server that receives alot of traffic (like several hundred hits a minute), performance is not an issue when delivering your average HTML page.