No, currently there is no way available to execute or require/import external Javascript files directly within a Logic Pro X script (most probably for security reasons). As a Logic Pro isn't a browser environment, you can't include script files from neither the local file system nor the web using a <script> tag. Even document.createElement() of the document object is unavailable for the same reason.

In short, Apple's implementation of the scripter runtime environment for the Logic Pro (X) does not allow to import/execute eternal Javascript files (as for now).