Need to add an average helper method to a NodeJS API

Hello, I already have an avg calculator but is very ugly and not efficient and need help to make it more efficient as a dynamic helper to be used in a different situation to calculate AVG of some rates. I also posted a question about it here: [login to view URL] I need it very fast as a need to keep the peace of my delivery. You will be asked to resolve it immediately after acceptance of the project. The system already makes AVG as described and showed in the question link above but I need that to be a helper method external and be able to use it when I will need to perform similar calculations Thank you