Injectjs: Javascript: How to call parent method of javascript file in child js file. Also how to include external scripts in the javascript file

I have 2 javascript files 1)ParentFile.Js 2) ChildFile.js. Now In ParentFile.js i have a method “CallParentMethod(param1, param2)”. In ChildFile.js i want to call the “CallParentMethod(param1, param2)” method. Also i need to include the external javascript reference in the ChildFile.js.

I am using injectjs activity to call the javascript file.
Can someone pls guide.

Issue resolved using a work around. Instead of calling parent function from child file, I have clubbed the code so parent code & child code is in same file.

Not sure how to import parent file in child file. If anyone has solution do share it. Thanks in advance.