Can't use data returned from ajax call in seperate .js file ????

Can't use data returned from ajax call in seperate .js file ????

I've been trying to figure this out for a long time (and thanks to those here who have helped) and I'm slowly getting how promise works in jquery (at least I think). My issue still seems to be using the return in another file...

So I have a file called request.js with this code,

function testAjax() {
    return $.ajax({
                  type: 'GET',                       
                  url: 'https://www.sciencebase.gov/catalog/items?parentId=504108e5e4b07a90c5ec62d4&max=60&offset=0&format=jsonp',
                  jsonpCallback: 'getSBJSON',
                  contentType: "application/json",
                  dataType: 'jsonp'
              });
}

var promise = testAjax();

and then I have a file called requestDone.js with this code,

promise.success(function (json) {
    alert(json.total);
});

When they are in the same file it works fine, but when I separate them it doesn't ??
The file for request.html refers only to the request.js script and the requestDone.html file refers only to the requestDone.js script.

What am I doing wrong ???