The short answer is minimal if any. There are several assumptions made regarding your question...first, that the code written is optimal itself. The main benefit of using OO JavaScript in my opinion is the ability to utilize
polymorphism and design
patterns in JavaScript. While I have not read anything stating there is overhead with loading the source, I can imagine that there is more overhead, than if the script was contained in the body to begin with, but that would defeat the purpose to begin with, since another desire is to modularize your code so you dont have cut-n-paste snippets everywhere.
