Framework: how to reuse functions in the core framework? javascript in this case

In a js framework there is a little problem: I want to reuse the code in the framework and outside it but it gets complicated;

when you want to add any klasses or helper functions it's done like this

 TStore.add({
      path: 'isArray',
      uses: ['inArray', 'someThingElse'],
      fn: function(l /*lib reference*/, u /* uses reference */){
           return function(array, item){
                /* stuff that calculates the array */
                return true; /* or false */
           }
      }
 })

now the problem is that when you call the method on TStore.add(...), this function will use the "inArray" that is the above function; I would like to reuse that code, instead of writing another time the same thing.

EDIT: The TStore.add method explanation

 TStore.add = function(o){
      (...)
      // here I need to use the "inArray" function
      // but I haven't it yet!
      // ex:
      var uses = o.uses;
      if(this('isArray', uses)){
           // do something
           // but "isArray" is not available before
           // I don't add it like this: TStore.add({...})
           // like the 1º script, above
   开发者_JS百科   }
 }

I think a lot of software (low level) finds this problem and is already solved, but I can't find a stable solution.

It seems like this problem could be solved by adding an extra layer of logic before you define TStore.add