On: The contents of a page is stored in the array page.allPageItems.
The same with a spread. spread.allPageItems.
If you want to filter all text frames of a given page, you could loop the allPageItems array of a given page.
Then ask every item if it is a text frame after you "resolved" it with getElements() like that:
if( myActivePage.allPageItems[i].getElements().constructor.name == "TextFrame" )
// do something.
There are other methods as well. You could loop the textContainers array of all given stories in the document and look for the value of parentPage. If this is identical to your active page store it to an array and when done with all textContainers of all stories loop the result array to do something with its contents.