Custom buttons and browser cache

the custom buttons have a part javascript and a part server php script.

When I upload changes made to the javascript part, to my webserver,

I have the problem with the webbrowser cache. Still the old javascript is executed.

Only if I press shift F5 to clear cache , it works fine.
Now there is the problem with my customers. They often forget to clear the cache.
Is there a pratical way for making updates with php runner with clearing the cache somehow ?