How to share filter between angular applications

How to share filter between angular applications

This is probably simple question, but I cannot figure the answer. I am
developing several angular apps, I want to have one javascript file with
all the filters I'm using.
Current I define the filters like this:
var app = angular.module('MyApp1')
app1.filter('filterCount',function() {
return function(input) {
....
}
})
How do I change my code to define this filter for any app that includes
this file (e.g., if I want MyApp2 to use it)? Is there a way to do this?
Thanks.