Multiple user controls with core javascript

Hi.

I'm in the process of building a "web user control" for a C#/ASP.Net application.  There will be any number of these controls on the screen at one time, and each one has a bunch of javascript within itself to set visibility of divs at runtime, depending on user inputs.

I was just wondering if there's a nice way of having a core of javascript that all the controls use, without having it repeated throughout the resulting web page when it's rendered?

Thanks in advance.

John.