How to extend the recipients.js of Email module

Dear Sugar Community,

The file is located at : 'modules/Emails/clients/base/fields/recipients/recipients.js '. 

In this file there are many functions and i want to customize one of them. 

I tried to copy and paste the file in the custom folder, to the path of : custom/modules/Emails/clients/base/fields/recipients/recipients.js, modifying the function I want and it Worked. 

Although, I want to create a new class that  extend the recipients.js file and modify only the function I want rather than the whole file....

The purpose of this modyfication is to include the 'E-mail" with the 'name' of the pop up dropdown when you click the " To" field at the "Compose E-mail" view. 

 I use version 8.0 of SugarCRM, but I am testing it at version 7.9.

The first priority is to extend the class in custom...

Any help is appreciated!!!